Advice on Heart rate Monitors

fdny9943

Is a heart rate monitor really necessary and if it is (or is helpful) can I wear one?

I'm 6' 2" currently weigh 315 down from 449 and I have a 54" chest.

I have just started Spinning and I love it and I think a HRM would help but am not sure and they are expensive.

Any "big" guys have any experience with them and does anybody know if there is a iPhone 4s app I can use in conjunction with a HRM?

Any brand/model recommendations? Thank you!!!