Free App for Apple Devices
 

https://cimg4.ibsrv.net/gimg/dodgefo...87c212fbf0.jpg

Found a free performance App that seems to be accurate, and uses GPS to record performance data of your car. Tried it out in my '14 Grand Caravan 3.6L and it recorded 15.6 in the 1/4 mile. Seems to be accurate compared to magazine test results! It's a fun App that's free.
Search for on the App Store, TRC (That Racing Channel)