I did a little research and found there are a LOT of these apps hitting the market. I personally have Dino Dyno, but it's complex and limited in its functionality.
Here are a few of the ones I found-no reviews, so "Caveat Emptor" should be observed.
Android
Trackmaster
"Trackmaster is a powerful racing lap timer that runs on your Android phone. Record your speed and times, analyze and replay your data, share your data on Twitter and Facebook, and export to Google Earth or MSExcel - plus much more! Works great for autocross, hillclimbs, road rally, and track days!" (EDIT: more details here)
Dynomaster
"Dynomaster is full-featured dyno and drag racing app that runs on your Android phone. It provides many functions including 1/4 mile times, power calculations, graphical analysis, G-meter, mapping, speech, import/export to Google Earth or MSExcel, sharing time slips on Twitter and Facebook - plus much more!"
Race Ace
"Race Ace provides datalogging for your car on a track or race day---lap times, course, maximum speeds, braking points and g-forces, based on data from the GPS."
Street Race
"GPS based Speedometer and timer for 1/4 mile drags and 0-60 mph sprints. Touch lights to start, wait for GPS fix and put the pedal to the metal when light hits green! Your time can be uploaded and results compared with other fast drivers."
Trackmeter
"The perfect tool for circuit regularity. Do your lap with as many as 99 references and then copy the lap to be the most regular. Ideal for regularity (TSD) in circuit or closed tracks. Allows to record the first lap to be able to copy the following laps. Also valid for trackdays/endurance."
iPhone
Track Day
"Track Day is an all-in-one tool for measuring your vehicles performance at the track. Using track day you can measure your vehicles acceleration times, record lap times automatically, and display real time cornering, acceleration and braking g-force information."
Dynolicious
"So you've already got a sweet ride... now you can measure just how sweet it is. Dynolicious uses the iPhone's built-in accelerometer to measure you vehicle's 0-60 acceleration, quarter mile elapsed time, horsepower, lateral G's, and several other performance metrics. A history of test results for your car are saved, so averages and trends can instantly be retrieved. Dynolicious also allows you to record modifications made to your car, and to evaluate the resulting gains (or losses) in power and performance."
Total Traction
"Total traction helps tune the most important performance system in your car—the driver. This is more than just another G meter. Total Traction provides continuous feedback about how close your car is to loosing traction, (skidding). It blends braking, cornering, and acceleration forces, and compares them to the car’s measured performance limits, while correcting for hills, banked corners, dips, etc., ensuring consistent and accurate results."
G Force
"G FORCE makes your iPhone or iPod Touch a handy vehicle G-Force meter. A nice looking enhancement to the dash of your car, too. Quantify the G-Force you experience in the vehicle (e.g. during acceleration, braking, drifting, cornering etc) or perform a quick dyno."
Harry's Lap Timer Pro
"Harry‘s GPS LapTimer is the iPhone tool for lap timing. Offering advanced data recording, it is the ideal companion for amateur racing. Utilizing GPS, LapTimer will automatically stop your laps and sector times. With laps stored in a database, you can track your progress while improving your lap times corner by corner. Using your existing iPhone, LapTimer is an extremely inexpensive option compared to standalone solutions."
Windows Mobile
TrakPal PitStop
"Analyse your performance using NMEA compliant GPS data recorded on your Pocket PC - the perfect complement to your GPS navigation software. Compare data from different runs to find where those important seconds were lost, whether on the track, training, commuting or just for fun. Zoom in and scroll graphs for speed, acceleration ? both laterally and forward/back ? and altitude. Graphs can be displayed either as raw recoded format or against distance. "
GPS Performance
"GPS Performance is a must have application for people with performance cars interested in performance statistics. Using a regular GPS receiver and sophisticated alorythms, GPS Performance is able to accurately measure 1/4 mile dashes and 0..60 timings. Circuits can be defined for timing laps and up to 5 split times per track can be added. Of course the runs are fully configurable, allowing custom distances and speed ranges to be specified, and tracks are created simply by driving around the circuit."
