I found this blogspot that has some cool hacking info on the following VTech systems. I've posted all the ones on this first page on this blogpost.
- Z80 Processor (Used in loads of VTech laptops)
- Genius Leader 6000SL
- VTech Parallel Buddy (Homebrew cartridge for various VTech laptops for custom code)
- VTech Genius Leader Dev Kit, VGLDK (Homebrew SDK for creating homebrew for the Genius Leader laptops)
- Genius Leader 4000 Quadro