I'm using genuine atmel programmers (currently I'm on jtagice3) been serving me fine for the last couple of years (also have the added benefits of being able to work together with gdb, so I can debug arduino code on my atmel sam D21 mcu)
Anyways, there are lot's of (cheaper) programmers out there, amongst others you could use another arduino as programmer..
@Nca78 Yes, I was actually thinking using DIP switch (or even more easy to read thumbwheel switch) to give a unique ID to each node! As soon as I receive the extra radio modules I ordered, I'll test that.
@Grubstake I'm afraid you're right! But it's ok to have just a few days of battery life. As I wrote, it might be often disassembled and reassembled.
@victus Im not familiar with this components you mention, you need to test yourself, cant help you with the technical stuff.
It does not seem to be a fully functional ECG but a heart rate monitor. As epierre said above, you need to define if you want to monitor or have a fully functional ECG, its a big difference. With a monitor all you get is pretty much your heartrate and you can detect arytmias. A fully working ECG is normally made with 12 leads and is used to in detail know how the electrical depolarisation from different time and direction/place within the heart muscle works. Holter is a example of a heart rate monitor over time.