One of my colleagues had a customer that was looking for a solution where they could have custom notifications on incoming emails.
That is they wanted to be able to light up the device, vibrate or make a specific sound if a message came in (say from your boss or a system alert)
We searched the web for a number of solutions and eventually found Watchflag.
Watchflag runs on mobile devices to scan incoming messages and alert you based on rules you define. It's like ringtones for your email.