Take a look at www.spen-soft.co.uk where you can download a fully functional ST7 programmer (with schematics & source-code), it works in standalone mode (keyfob) or connected to a pc via RS232.
I have been working on this for a while and have decided to share my work with everyone. It is capable of progamming all CFlash/XDFlash/HDFlash devices including USB devices. Whats best of all is its completely free with source-code. The only thing I ask - If you make any changes/updates please email them to me. Regards SJO