If you could get at the actual pins in the micro:bit that go from the nRF51 to the USB interface then you might be able to use a USB-TTL converter...
I've got one of the new micro:bits coming (ordered yesterday) so I'll try and look into this in a bit more detail
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
If you could get at the actual pins in the micro:bit that go from the nRF51 to the USB interface then you might be able to use a USB-TTL converter...
I've got one of the new micro:bits coming (ordered yesterday) so I'll try and look into this in a bit more detail