Android Question Electrocardiogram

1) Search for heart rate sensor board
2) Choose the way (interface) you need for Android device to get the data: USB port, Bluetooth or WiFi-internet connection.
3) Choose a microcontroller (MCU) that can read the sensor and pass the data to Android device or an Internet-accessible server.
4) Make a MCU program (sketch) for reading the sensor: simplest way is Arduino or B4R that works over the Arduino. If with the server - sending HTTP requests to the server.
5) If WiFi-connection - make B4A Android app to read data from the server by Android device via WiFi-internet connection. Or make app for USB wired or Bluetooth wireless connection to the MCU.
6) If server is used - make the server side script (program) getting the data from MCU. And, maybe, the database for storing data flow.