My brother and I both use Collett 900 Communicators. We bought them new last year. We both have Modular Helmets. You can see, somewhat, my Collett with my Modular in the attached photo. The hook-up was elementary. The battery life is about 9 hours on them. The piece of mind of knowing everything, that your partner sees around him and you can be communicated instantly, is invaluable. Last year in Paradise MI, three careless sledders we going way faster than what they could handle around a curve, and crossed the invisible middle line. My brother was in front of me by 200 yards, and told me of the impending danger. I quickly moved over to the side, off the trail and was narrowly missed. One other great aspect of the Collett Platinumn is that you can hook up a MP3 player or a cell phone to it. I listen to 8 hours of music on my MP3 through the Collett Speakers while riding. If my brother says something to me while the music is playing, the music stops and his voice cuts in automatically. When he's done speaking, the music resumes. When we got close to the groomers the beacon sound was unmistakable! I highly recommend these!!!!!!!!!!!!!!!!!!!!!!!
Also, NEXTEL in Michigans UP is as good as teets on a bull.