iOS - You can choose from different ones online that you can connect your iOS device to you PC and will work. You can use QuickTime Player if you have a Mac computer and iPhone/iPad, if you don't you can use this - https://airmore.com/record-ios-screen.html This is definitely not the best screen recorder, though it is free and works okay.

Android - https://play.google.com/store/apps/details?id=com.hecorat.screenrecorder.free

Recorder- Another thing to add is that you may need a stopwatch. You don't need one, but it makes my job easier to judge your time https://play.google.com/store/apps/details?id=de.jentsch.floatingstopwatch