One of the things I have a lot of difficulty with is hearing when my cellphone is going off and making sure I can answer the phone in a timely manner. Most people I know assume I won't be answering the phone when they call. I so rarely hear it, not to mention I'm flakey about turning it off silent/vibrate when I get off work.
Right now I have the Streamer, which pairs with both my hearing aids and my phone to alert me when a call comes in. Of course, I still have to be wearing the Streamer. There are a couple of neat options I've seen which will work with any phone that has Bluetooth enabled. Both are available on ThinkGeek, one of my very favorite online stores.
The first option is one I actually own, the BluAlert Bluetooth Bracelet. Scotty got this for me last Christmas. After pairing the bracelet with your phone, as long as the bracelet is within range of the phone it will vibrate when your phone rings. The only downsides I found to the bracelet were that it is quite a bit too big for my wrist, and the range is small. Basically I need to wear my phone on a holster or keep my purse nearby if I want to use the bracelet, and if my phone is on a holster I can simply put it on vibrate and be assured of being aware of a call.
The other cool option is this Bluetooth Watch with Caller ID Display. The watch vibrates on a call, and has the bonus features of showing you who is calling and potentially muting the ringer. Plus the leather band is adjustable so the problem with the bracelet would not be an issue here.
I'm sure there are other interesting products, and as I see them I'll blog about them. These two options are certainly nice!