diff --git a/apps/bthrv/ChangeLog b/apps/bthrv/ChangeLog
new file mode 100644
index 000000000..0e51186a4
--- /dev/null
+++ b/apps/bthrv/ChangeLog
@@ -0,0 +1,11 @@
+0.01: New App!
+0.02: Make overriding the HRM event optional
+      Emit BTHRM event for external sensor
+      Add recorder app plugin
+0.03: Prevent readings from internal sensor mixing into BT values
+      Mark events with src property
+      Show actual source of event in app
+0.04: Allow reading additional data if available: HRM battery and position
+      Better caching of scanned BT device properties
+      New setting for not starting the BTHRM together with HRM
+      Save some RAM by not definining functions if disabled in settings
diff --git a/apps/bthrv/README.md b/apps/bthrv/README.md
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index 000000000..8a80b0fd4
--- /dev/null
+++ b/apps/bthrv/README.md
@@ -0,0 +1,11 @@
+# Bluetooth Heart Rate Variance
+
+This app uses [BTHRM](https://banglejs.com/apps/#bthrm) and can calculate the HRV if the used bluetooth heart rate monitor delivers interval data.
+
+## Usage
+
+Just install and start the app. Select button resets the already measured values.
+
+## Creator
+
+[halemmerich](https://github.com/halemmerich)
diff --git a/apps/bthrv/app-icon.js b/apps/bthrv/app-icon.js
new file mode 100644
index 000000000..4d4cf6354
--- /dev/null
+++ b/apps/bthrv/app-icon.js
@@ -0,0 +1 @@
+require("heatshrink").decompress(atob("mEwwJC/ABUMAokcAq0eAok+Aok2AgcCm0EAoUHmw2DAoMOAgMDh9jEgPAg/98cfn/gg/58cbv/ggcB8cz8HADIPjmIECgHB8OAAoVB8AFDgPgIQcBCwYFMAH4ARA"))
diff --git a/apps/bthrv/app.js b/apps/bthrv/app.js
new file mode 100644
index 000000000..7f6ec2d35
--- /dev/null
+++ b/apps/bthrv/app.js
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+var btm = g.getHeight()-1;
+var ui = false;
+
+function clear(y){
+  g.reset();
+  g.clearRect(0,y,g.getWidth(),g.getHeight());
+}
+
+var startingTime;
+var currentSlot = 0;
+var hrvSlots = [10,20,30,60,120,300];
+var hrvValues = {};
+var rrRmsProgress;
+var saved = false;
+
+var rrNumberOfValues = 0;
+var rrSquared = 0;
+var rrLastValue
+var rrMax;
+var rrMin;
+
+function calcHrv(rr){
+  //Calculate HRV with RMSSD method: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5624990/
+  for (currentRr of rr){
+    if (!rrMax) rrMax = currentRr;
+    if (!rrMin) rrMin = currentRr;
+    rrMax = Math.max(rrMax, currentRr);
+    rrMin = Math.min(rrMin, currentRr);
+    //print("Calc for: " + currentRr);
+    rrNumberOfValues++;
+    if (!rrLastValue){
+      rrLastValue = currentRr;
+      continue;
+    }
+    rrSquared += (rrLastValue - currentRr)*(rrLastValue - currentRr);
+    
+    //print("rr²: " + rrSquared);
+    rrLastValue = currentRr;
+  }
+  var rms = Math.sqrt(rrSquared / rrNumberOfValues);
+  //print("rms: " + rms);
+  return rms;
+}
+
+
+function draw(y, hrv) {
+  clear(y);
+  var px = g.getWidth()/2;
+  var str = hrv.toFixed(1) + "ms";
+  g.reset();
+  g.setFontAlign(0,0);
+  g.setFontVector(40).drawString(str,px,y+20);
+
+  for (var i = 0; i < hrvSlots.length; i++){
+    str = hrvSlots[i] + "s: ";
+    if (hrvValues[hrvSlots[i]]) str += hrvValues[hrvSlots[i]].toFixed(1) + "ms";
+    g.setFontVector(16).drawString(str,px,y+44+(i*17));
+  }
+  
+  g.setRotation(3);
+  g.setFontVector(12).drawString("Reset",g.getHeight()/2, g.getWidth()-10);
+  g.setRotation(0);
+}
+
+function onBtHrm(e) {
+  if (e.rr && !startingTime) Bangle.buzz(500);
+  if (e.rr && !startingTime) startingTime=Date.now();
+  //print("Event:" + e.rr);
+  
+  var hrv = calcHrv(e.rr);
+  if (hrv){
+    if (currentSlot <= hrvSlots.length && (Date.now() - startingTime) > (hrvSlots[currentSlot] * 1000) && !hrvValues[hrvSlots[currentSlot]]){
+      hrvValues[hrvSlots[currentSlot]] = hrv;
+      currentSlot++;
+    }
+  }
+  if (!saved && currentSlot == hrvSlots.length){
+    var file = require('Storage').open("bthrv.csv", "a");
+    var data = new Date(startingTime).toISOString();
+    for (var c of hrvSlots){
+      data+=","+hrvValues[c];
+    }
+    data+="," + rrMax + "," + rrMin + ","+rrNumberOfValues;
+    data+="\n";
+    file.write(data);
+    saved = true;
+    Bangle.buzz(500);
+  }
+  if (hrv){
+    if (!ui){      
+      Bangle.setUI("leftright", ()=>{
+        resetHrv();
+        clear(30);
+      });
+      ui = true;
+    }
+    draw(30, hrv);
+  }
+}
+
+function resetHrv(){
+  hrvValues={};
+  startingTime=undefined;
+  currentSlot=0;
+  saved=false;
+  rrNumberOfValues = 0;
+  rrSquared = 0;
+  rrLastValue = undefined;
+  rrMax = undefined;
+  rrMin = undefined;
+}
+
+
+var settings = require('Storage').readJSON("bthrm.json", true) || {};
+
+g.clear();
+Bangle.loadWidgets();
+Bangle.drawWidgets();
+
+
+if (Bangle.setBTHRMPower){
+  Bangle.on('BTHRM', onBtHrm);
+  Bangle.setBTHRMPower(1,'bthrv');
+
+  if (require('Storage').list(/bthrv.csv/).length == 0){
+    var file = require('Storage').open("bthrv.csv", "a");
+    var data = "Time";
+    for (var c of hrvSlots){
+      data+="," + c + "s";
+    }
+    data+=",RR_max,RR_min,Measurements";
+    data+="\n";
+    file.write(data);
+  }
+
+  g.reset().setFont("6x8",2).setFontAlign(0,0);
+  g.drawString("Please wait...",g.getWidth()/2,g.getHeight()/2 - 16);
+} else {
+  g.reset().setFont("6x8",2).setFontAlign(0,0);
+  g.drawString("Missing BT HRM",g.getWidth()/2,g.getHeight()/2 - 16);
+}
+
+E.on('kill', ()=>Bangle.setBTHRMPower(0,'bthrv'));
diff --git a/apps/bthrv/app.png b/apps/bthrv/app.png
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index 000000000..7a45b9c42
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diff --git a/apps/bthrv/metadata.json b/apps/bthrv/metadata.json
new file mode 100644
index 000000000..6a8e7e940
--- /dev/null
+++ b/apps/bthrv/metadata.json
@@ -0,0 +1,17 @@
+{
+  "id": "bthrv",
+  "name": "Bluetooth Heart Rate variance calculator",
+  "shortName": "BT HRV",
+  "version": "0.01",
+  "description": "Calculates HRV from a a BT HRM with interval data",
+  "icon": "app.png",
+  "type": "app",
+  "tags": "health,bluetooth",
+  "supports": ["BANGLEJS","BANGLEJS2"],
+  "readme": "README.md",
+  "storage": [
+    {"name":"bthrv.app.js","url":"app.js"},
+    {"name":"bthrv.recorder.js","url":"recorder.js"},
+    {"name":"bthrv.img","url":"app-icon.js","evaluate":true}
+  ]
+}
diff --git a/apps/bthrv/recorder.js b/apps/bthrv/recorder.js
new file mode 100644
index 000000000..0fce6971e
--- /dev/null
+++ b/apps/bthrv/recorder.js
@@ -0,0 +1,51 @@
+(function(recorders) {
+  recorders.bthrv = function() {
+    var lastGetValue = 0;
+    var lastUpdate = 0;
+    var rrHistory = [];
+    var hrv = "";
+    function onHRM(h) {
+      if(!h.rr) return;
+      if (lastUpdate + 3000 < Date.now()){
+        rrHistory = [];
+      }
+      rrHistory = rrHistory.concat(h.rr);
+      lastUpdate=Date.now();
+    }
+    return {
+      name : "BT HRV",
+      fields : ["BT HRV"],
+      getValues : () => {
+        if (lastGetValue + 10000 < Date.now()){
+          lastGetValue = Date.now();
+          
+          if (rrHistory.length > 0){
+            if (rrHistory.length > 1){
+              var squaredSum = 0;
+              var last = rrHistory[0]
+              for (var i = 1; i < rrHistory.length; i++){
+                squaredSum += (last - rrHistory[i])*(last - rrHistory[i]);
+                last = rrHistory[i];
+              }
+              hrv = Math.sqrt(squaredSum/rrHistory.length);
+            }
+          }
+        }
+        result = [hrv];
+        hrv = "";
+        rrHistory = [];
+        return result;
+      },
+      start : () => {
+        Bangle.on('BTHRM', onHRM);
+        if (Bangle.setBTRHMPower) Bangle.setBTHRMPower(1,"recorder");
+      },
+      stop : () => {
+        Bangle.removeListener('BTHRM', onHRM);
+        if (Bangle.setBTRHMPower) Bangle.setBTHRMPower(0,"recorder");
+      },
+      draw : (x,y) => g.setColor((rrHistory.length > 0)?"#00f":"#008").drawImage(atob("DAwBAAAACECECECEDGClacEEAAAA"),x,y)
+    };
+  }
+})
+
diff --git a/apps/bthrv/screenshot.png b/apps/bthrv/screenshot.png
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