Back in April I made a reaction time tester. This christmas I made a completely revised version for a christmas present with new game mode, a wooden enclosure and much more battery efficient operation. Check out the videos below and head over to my blog at http://petenpaja.blogspot.fi/2013/12/speed-tester-v20.html for a full technical write up, schematics and more.
Speed tester: http://www.youtube.com/watch?v=zpzQddvW0Ms
Memory tester: http://www.youtube.com/watch?v=qhKSChhsOAs