Harry's Lap Timer Pro
 

Hello, wanted to post a plug for Harry's Lap Timer Pro app for iPhone. I velcro'd my phone to the dash of my 944T using a modified phone case, velcro on the dash and case so I could just pop my phone out after the session. I put in the Points Of Interest on the Google Map within the app a few days before I went to the DE. After turning on the app and selecting the track set (you can download certified sets for most popular North American Tracks) - the lap timer starts after you pass the POI trigger and then times every lap until you hit stop. It has an awful lot of functionality for the cost if you already have the phone. You can see lateral/longitudinal g-loading (I learned that I am a wuss when it comes to threshold braking) as well as corner entry and mid-corner speeds. I have no financial interest in the product but was so impressed I just wanted to share.

Yeah, it's a pretty cool app. The biggest issue is that the iPhone's GPS is pretty weak, both in performance and in reception... Putting it on the dash, so that it has a clear view of the sky through the windshield, seems to work the best. If you put it in the center of the car, reception gets really poor.

They claim that if you buy the Tom Tom mount, not only do you have a mount, but it improves the GPS.