I’ve got a Kickstarter project going (and now funded) to bring new components to the old Parallax BASIC stamp. It was a good product in its day 20 some years ago, but was a dead end. I propose adding a USB embedded ARM in the same form factor and pin out and bringing that to market as an open source hardware platform. Love to see Sparkfun sell and/or build it.
Through the USB it can be programmed in C/C++ with mBed or gcc tools. Also in BASIC. Add an optional JTAG and it can act as a SW debugger, or be set up as a SW target which gives access to Keil, IAR and MCUxpresso tools.
http://basicchip.com/rev2lifesize.jpg
Kickstarter–