This is a sorta-clever technique ... but if you can't have your phone, this is 100% useless
There are only three proper ways to worry about how much time you have left on a test:
- don't worry: keep going until you're done or you run out of time (the best option)
- wear a watch
- periodically look at the countdown timer on the test (if it's either being done on a computer, or if there's a timer in the room)