I (relatively) recently received a handsfree bluetooth rearview mirror kit as my prize from Community-Credit.com.
This weekend, I finally got around to hooking it up. First impressions are good. The mirror just clips right on top of the existing mirror and is held in place by some spring loaded clips. I like the fact that this mirror is about 25% wider than my original mirror, giving me a better field of vision. The mirror does seem darker though, but not so much to be a problem.
Pairing the bluetooth to my phone was quick and painless, and a small blue led lights up when connected. On the side of the mirror is a small earpiece that connects via magnet. So you can use the speaker on the mirror or the earpiece for more privacy.
Sound quality is acceptable, and if you have voice tags set up on your phone, the hands free dialing is nice too although I had to speak pretty loud for it to recognize the voice tag.
I don't know how long battery life is because I haven't driven anywhere long enough for it to get a full charge... so far I've been keeping it plugged into the lighter. If the charge light ever goes out, I'll unplug it and see how long it lasts.
The incoming calls feature is kinda cool, since it shows caller id on the mirror surface. I've tested the incoming calls a few times and it's kinda nice just hitting a button on the front of the mirror.
All in all, I'm a bit of a gadget geek so I'm pretty happy with it. I've seen these things go for around $100 at MicroCenter, which is probably more than I'd be willing to pay. If the price goes down though, it's worth snatching one up.