I thought this might be of interest to some of you. It's not mine but I work with the creator's brother who is running it in their Chump Car this year.
https://play.google.com/store/apps/...pperlite&feature=more_from_developer
It is basically a GPS based lap timer for your phone that will analyze each of your laps. You can also interface with a Bluetooth OBDII adapter to overlay engine data or use a higher frequency external GPS unit.

For those doing endurance racing or extended track days, you can also easily transmit the data back to your pc in the pits through wifi as well as receive messages from the pits. (Pitside app for PC)

They are planning to have it out for further testing this Friday at Shannonnville.
I already have the OBDII adapter so I may give it a try as well.

Should also add link to his website:
sites.google.com/site/wifilapper

I've looked into phone-based GPS/lapping software and the problem with them is that the GPS in our phones has a very low refresh frequency compared to a commercial unit (standalone GPS or more specifically, GPS capable dataloggers) and so lap times can vary greatly and the room for error is large. The other features are definitely nice and overlaying them with the track - errors or not - will still give a good idea of how things are going.

When I get a new phone one of these days I'll have to give it a try.

That's why this one seems decent as you can interface it using a higher refresh rate standalone Bluetooth GPS if you want better accuracy.
I'll have have to catch up with Phil on Monday and see how they made out. They were running the long track just before we showed up so I was hoping to see him out.

Sounds good then, because that was really my only concern. Keep me/us updated with how it works out for Phil. A cheap, fully-capable GPS/data-logger is a wonderful thing. Been wanting one for a while for my track days.

Bringing this back again. With the reliability of the timers at Shannonnville, I'm going to install this as a backup plan. I heard the developer added a 'point to point' option for people that don't complete a full lap, like drag racers or one lap.
I should have it working for Sunday.

It keeps telling me its waiting for the GPS but its on.

OK i got it to work, but it wants me to go back to the start/finish line after I run a 1/4 mile.

Anyone playing with this?

I think that's the way it's supposed to work. Because it uses the GPS it basically has a start and stop point defined and it measures the time it takes to get from point to point.
It doesn't use interpolated speed like other systems.