SplitTime

Wanna measure how fast you are? Wanna measure your Stones in Curling?
With this app you can use the fancy Android-Camera-Photocell-Sensor ( Camera only actually :P ) to do exactly this.

Set up two Android Phones with this app and connect them over a WLAN (a Hotspot does the job if nothing else is around) and start measuring.

This app uses the front cameras of phones to detect if something crossed it's central line.
One phone is at the 'Start' (Back) line and the second one at the 'Finnish' (Hog) line.
The second one shows how long you took after you have passed it.

The namings like backline and hogline are from Curling, as I have developed it for this sport. Try it out with this app too :)
But of course you can use it for any other Measurements too.