I'm doing a portable ecg eck visualizer , the idea is to develope a low cost device that can be taken to remote places and even nearby places where the access to this kind of equipment is difficullt. the device is powered by a 18650 battery, using a msp430 to sample the signal, since the esp8266 board that I have doesn't have an ADC pin I choose to using the msp, so the data is send from the MSP to the ESP and then show in the oled.
the device also show the signal in the pc using procesing to get a better visual of the signal, I'm planning to transfer the app to a smartphone, if so the oled will be not requiered.