Initially I was a bit unsure about getting this app given the cost (£19.99) however after using it the cost is definitely worth it over the course of a season.
As long as you have a decent 3G or wireless connection you get live timing information from all practice sessions, qualifying and the race. You even get an interactive 3D race track that shows you where each driver is on the track. You can even rotate the track around using your finger to get different angles if you want. You can also view a table which shows all the sector times of each driver.
Coupled with that you get all the driver standings, manufacturer standings etc.
£20 may seem expensive however look at it this way it's just over £1 a race for a full season.
Works well on the iPhone but if you have an iPad it really comes into it's own.
Example of iPad in Portrait. (landscape puts the track full screen with driver order list at side)
Carl