There's a host of handheld units you can purchase. SCT and Hypertech have "canned" tunes.
HP Tuners and EFI allow you to tune your own car with much more options and a scanner to see the effects of the changes.
specializes in the following high performance cars and heavy duty trucks for tuning:
•1997-2011 Chevrolet Corvette C5 & C6 including ZR1,Grand Sport,Z06s
•1998-2011 Chevrolet Camaros Generation 4 and 5 Z28, SS, RS
•2002-2011 Cadillac CTS, STS, XLR, SRX, DTS, Escalade
•2000-2011 Avalanche, Hummer, Tahoe,Suburban, Yukon, Silverado V8s
•1998-2002 Pontiac Firebird, WS6, Trans Am
•2003-2004 Chevrolet SSR 5.3
•2004-2006 Pontiac GTO