Heart Rate Monitor - Suggestions?

I want to purchase a heart rate monitor to use while I exercise - currently doing Insanity, but just not sure which one to get. I know the ones with the chest strap are supposed to be more accurate, but beyond that I am at a loss. I ordered one from Amazon, only to find that it was made specifically for walking/jogging and you had to enter your stride length for it to calculate calories burned. Does not work with Insanity. So back to square one and don't want to waste any more money on something that isn't going to meet my needs. Any suggestions/help would be greatly appreciated!!!!