I agree with Gary, I use the Mychron 4 with the GPS option and love it! The GPS helps pinpoint problem areas that you’re having on the track. The Race studio program that you download onto your laptop is phenomenal IMO. the GPS works well for 2 reasons I think, 1) the lap timing device at our track seems to be hit or miss whether its working/counting laps so we didn’t always get our information correctly and with the GPS option you don’t have to relies on the tracks components to make the system work. 2) When you overlay lap over lap on top of each other it gives you the ability to show your 13 year how consisted he is in each and ever turn and by seeing this you both can figure out together the fastest way around the track.
I also agree with Walt EGT is way more useful as a tuning tool then CHT.