When buying my cars - I always do an HPI check as most people do. The last time I done an HPI check I used a company called iCarcheck and you get your report in PDF format etc.
I've just received an email from them today to say they're launching an iPhone app and it's free to register and FREE GOLD checks until 2nd January (usual price is £4.99 each) - you can get i here:
App Store - iCarCheck
Just installed it and checked it on mine again and it was spot on! - if you're in the market for a new car or want to check your car history and have an iPhone then I wouldn't hang about as it'll be gone soon!
EXAMPLE PICTURES OF APP: