Buy a Playdia, make a CD image, get a hex editor and go to town. Since people aren't even sure what processor it uses, you'll have to do some RE work.
I always wondered how that worked... but living in CD-i country, maybe I'll even come across a devkit someday
CD-I? Are you saying that the Playdia is a CD-I system? Or, it's about as useful as developing for the CD-I?
I don't know anything about Playdia, but if it's similar to CD-I, then *I think* that system uses a 68000 (or maybe a 68010) and runs something like OS9. I had an interview with Phillips in Surrey to work on CD-I development (must have been around 1991). Glad I didn't get the job there (probably because I argued with the studio head that 12fps was not good enough) considering how well it did in the UK (I think I saw it for sale once). Had an interesting tour round the factory though.