Well, a lot of people here seem to think you don't need thermometers, because they learned from their caveman neighbor as a kid how to stick their finger into the meat and know the temp by how much it hurts, and can tell the temp of a grill by sticking their hand in and seeing how long until it catches fire...
And a lot of them will give you the option to get a second mortgage on your house and buy a specific thermometer. Some say red, some say green... If you're going this route, though, you probably should get a pink one and work your way up to the more extreme colors.
For an instant read you'd probably be fine with something like this:
http://www.amazon.com/Taylor-9842-C...meter/dp/B00009WE45/ref=tag_tdp_ptcn_edpp_url
Or you can get the kind you stick a probe in and leave it in for the whole cook, like this:
http://www.amazon.com/Polder-Classi...phite/dp/B000P6FLOY/ref=tag_tdp_ptcn_edpp_url
Personally, I bought a cheap one like the second one, and I used it several times before I just replaced them with a seat-of-the-pants "gee, it's been a long time, let's poke it with a stick" method that works for me. Now that I think about it, this should concern me, because I *love* gadgets. Maybe I should see a doctor about my lack of interest in thermometers!
In short, there's no end to the gadgets you can get, and quality may make your cooks better, but you pay for it. Or you can go caveman and just guess. I'm not here to tell you what works for you.