Fastfwd

I just got a new bike and alredy had a trainer. Now I want to know how to use it best.

It seems like hearth rate is very important. I guess I should get a HRM but I would also like to know what I have to watch for in my hearth rate.

Also I was expecting to use my GPS with the bike but it's useless on a trainer.

Are there any cycle computers that will give me HRM and work on the rear wheel(trainer)?

Or am I better off getting just a HRM watch? And maybe a little cheap wired computer for the trainer?

Where do I read up on hearth maximum rate and how to burn fat?

Thanks