I'm thinking about getting a Heart rate monitor, to help training for this 300k round a lake ride. I'll probably only get a cheap little thing (moving house etc has left me a bit poverty stricken!) And I'll probably only use it 'till the summer - then I'll forget I've got it ... Apart from the obvious heart rate, is there anything that a HRM MUST have. Is it best to get one that sits on the handle bars? Do they all use a belt round the chest? Are they all wireless? As you can see I have no idea what I'm looking for!