Heart rate monitors, compatable bras, what do I do?

Okay so. I am purchasing a heart rate monitor off of amazon. Now, I am new to this whole fitness business and am trying to get myself into it. I do little work outs at home and I do Zumba. I'm tired of trying to calculate and probably being wrong in terms of calories. While browsing them in amazon I came across several that seem to fit what I need, but because I have no idea what I'm looking at and going in blindly I need help. I saw Polar FT4 Heart Rate Monitor and it has high ratings. It aslso falls into what I'd be willing to spend. What do you think of it? Or are there any other good ones I should take a look at prior to buying? I just want something that will obviously track my HR but also calories burned. I don't need it to log or store work outs or anything schmancy like that.

Second question: I also saw a sports bra that had a built in HRM that said it was compatible with other HRM. now. Only 7 people reviewed it and three people commented on it. Was almost given 5 stars. Only one person gave it a three in terms of when she went running, the built in thingy kept popping out the one side. She said she was a little chesty but didn't specify how chesty. I would consider myself chesty but others prob wouldn't so not much to go with there. So. Have any ladies had experience with something of this nature? Applies to men if there are work out shirts that have them built in. (Again, new to this whole thing, don't know if they exist).