Go to digimoto.com to check out their software.
While not just for the Boxster this software will return real-time data on whatever the car is sending to the OBD II connector.
It will also do 0 - 60 time, 1/8 mile time and speed, 1/4 mile time and speed.
They also have a screen with 7 gauges and a page where you can chart up to 4 parameters in real time. A laptop is the way to go.
It's relatively inexpensive.
Some of the data that is displayed can be seen here:
http://digimoto.com/images/main.jpg
Regards,
derb