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.
You can try it for Free or buy it at 50% off at the moment!