The NetYaroze was (is) a black playstation with additional memory and a paralell link to your PC - and a copy of the cross compiler environment (... CodeWarrior? I think) and some basic libraries.
It had a fair developer community, and is a part of Sony's avowed drive to create and sustain a garage developer scene - in order ot have more professional developers interested in it in the years to come.
I think a lot of people bought it just to have a black bagel toaster though ;)
Oddly, though this developer scene continues with the linux PS2, that offerring does not offer as complete access to the graphics libraries and such that are needed to develop games. Which is a real shame (but it does have a hard drive, meaning you can run full CD images)