Yea you can't really modify anything, but you can read codes as well as live data which shows the exact numbers the sensors are outputing, which can be used for diagnostics or to modify other things to dial in the exact values you want. Depending on the app you use you can do true 0-60 numbers or 1/4 mile times. Or even a calculated estimated HP and TQ numbers. Also there are MPG instant and average values.
Heck just for an OBDII code reader is $50 at most places. For $15 you get more with this setup.