My first master thesis was a ECG system that was supposed to communicate with the PC or PPC by bluetooth. It turned out rather well (except that the enclosure was a bit rough). The hardware was a self designed pcb with st-micro arm7 processor. It runs FreeRtos and some nice features- adc does most of signal acquisition with DMA up to the point of putting it all in the queue. All the design files and master thesis pdf is given below.
The pdf file with the while ECG masterthesis. (Good place to start)
The second thing is Altium designer files with the schematic and pcb: Altium pcb and schematics.
A viewer to see the data in wave form representation: viewer PPC i PC.
Workspace with source code for eclipse with ARM Code sorcery compiler is here: sourcecode.zip.
You may need sources for FreeRTOSV5.2.0, code sorcery arm lite compiler suite to compile the sources, and some way to put it in the processor if you would like to play with the code. I have it all somewhere if anybody is interested, but it should be easily available on the net. I used usb-uart 3.3v converter to upload the code(no way to debug by wire in my case).
The signal flow based on timer triggered ADC and DMA transfers
PCB was designed to be compact and keep the most noise sensitive signals far from DC/DC converter.
What is also interesting is the organization of different tasks- some were responsible for ADC and some for menu on lcd and button debouncing.