Side project of today:
Build a lap timer for my son + friends for their BMX track!

Maybe runners can also use it.

@Jumpshot44, yes it can be used for runners as well!
@Haxk20, nope I will use an Arduino, plywood, a bunch of clothespins, duct tape and some 7-segment displays. My estimate is that the construction will stand ~5 mins of playtime. I will however reap the benefits of being named "best dad ever" by my son and all his friends, and I will without hesitation blame them for being careless and breaking the device, muhahaha. 😀😁