The Torque App with a cheap Bluetooth OBD2 dongle (down to about £7 these days), and an old Android phone, is a great thing to have to hand, I have used it on my different model Audi's and other cars such as BMW, and some Mercedes, for what is effectively pennies, you've got a decent and quite a sophisticated tool!
You can measure many things and use it like a DIS with 'more' features than a standard DIS.
It can have a few issue's like a little lag, but all in all it is a great tool, in fact for the price, I'd say it is a must have for everyone here, as your guaranteed that will need to read fault codes at some point
I know it isn't as sophisticated as VCDS which is a different beast altogether, as it won't allow you to tap into other control modules, but if you have a fault with the engine, it certainly picks that up, which is the main point of getting you out of trouble and keeps your wee beasties going
Cheers
Sarge
EDIT: May not work on the A2