Great, what is the best I can buy for the external gps and wireless obd? Thanks

Hi Harry, I just downloaded Harrys Laptimer Pro. I have an Iphone 4s. I like the Verizon suction cup mount better than the tom tom for the phone. Do I need to purchase some type of gps or other device for this to work in my race car or will your program work with just the iphone?

Thanks