Just got an Alivecor - had it shipped from the US as its the new generation model.
This works very well with an ipad and is easy to set up - so no need for a phone.
I did a baseline ECG test and sent it off as a matter of interest - costs 5 quid and came back within 5 minutes! I am sinus rhythm but braccardiya (spelling?) as my resting heart rate is around 55 but all normal.
You need to sit very still when doing the EC as its very sensitive to movement.
I think this is a very useful tool - not to be obsessive but a good tool to check if you think your hear has gone out of sync.