This is an Android App that uses the front camera to detect when an object traverses a certain (virtual) line in front of the camera. It can be used everywhere without special equipment, only 2 phones. Depending on the duration it is used, the phone battery can be drained fast. I recommend using it on OLED displays, since the displays get black with this App when not used to display something important and thus minimize the power drain on OLED displays. Maybe connecting a powerbank is a good idea.
When run on 2 Phones, connected over WLAN (Hotspot on one is enough), one can be set up at start and the other at the finnish line. The first phone then sends a signal for the start time, the second stops it and displays it on its display immediately.
This can be used for all kinds of sports or time measuring applications, but it is mainly intended for Curling. Thus the namings, one phone can be set up at the Back(/Tee)line, the other at Hogline to measure the splittime.