If you're performing, go with Shure or AKG with multiple channels.
If you're just using it for personal use, Audio Technica makes a good unit. Whatever wireless transmitter you get though, make sure it has AT LEAST 2 channels. They use UHF frequencies (same as TV channels), and if you have a strong signal comming in over your single frequency, you won't be able to move more than a few feet away from your base.