Figure 1: Block diagram of ECG device architecture. Not all components are neccessary.
A comparison has been done between three OS ECG devices: MobilECG, GammaCardion, Olimex
Here are very brief summaries on all three devices, listed in the order of most to least appropriate/useful.
MobilECG uses the phone app, communicates via TiWi Bluetooth module. It is by far the closest to what we want, design wise and capabilities-wise. I recommend taking it's framework and working from there. After a few more attempts I remained unsuccessful in getting in touch with any of the people involved in this project but was successful in recovering most of the design files and documentation from the web. The whole AFE is on a microchip. I got hold of the microprocessor that is used in mobilecg and am currently in the process of putting it together and checking out their firmware. The firmware is fairly complex and until we are able to flash it onto the processor we are unable to tell whether the firmware complete or not. This will still take some time as it's a quite complex environment.
Olimex is not a full ECG device per se, rather it's an Arduino shield containing the AFE hardware. The digital part is then done on Arduino. It is a platform for a 5-lead ECG. The only way we could use it is by stacking them up which certainly has drawbacks. It's a solution, but it's not the preferred one.
GammaCardio is used with a PC. A design of this device is rather old and is not up to current standards. I do not recommend spending much time with it. The most interesting part of it is that it has the CE certificate.