Movius Interactive has created an application that will detect when you have lost a call due to a weak signal, and will automatically reconnect once a reliable signal is available. No need to redial. You will hear a tone. A pop-up window will appear letting you know your call is being reconnected and giving you the option to cancel the call.
If you live in an area where you experience dropped calls, this sounds like a viable solution, or a least something to ease your frustration a bit.
Snapback is available on BlackBerry App World for $4.99
How does it know the difference between a dropped call and a hang up.
I get dropped calls when talking to my Mom a lot (she gets bad reception in her house) and then we play the who's calling who game for two minutes ...or... the "you didn't call me back" blame game several minutes later.