Multi-threading?

That's right. Actually, when I looked at Tessel's add-on board animation which gets inserted on the MCU board, it reminded me of the impractical USB custom devices: when plugged in the first time: It's plug and pray because compiled drivers need to be found (on top of being admin)... for the host (win, iOS, Android, Linux...)

Would developers' life be easier if each "shield" comes with an EEPROM which contains the javascript drivers and web pointers (where to get spec, upgrades etc...), so the platform (whatever the MCU) can use it right away, like dynamic added resource? This would justify interpreted language implementation for portability.

By the way, surveying around, got some questions:

• What are the pros and cons of embedded Javascript vs eLua (which could be precompiled)?
  
• Can Espruino's interpreter get extensions that would allow specific boost of performance for MCU embedded applications? (because maybe supporting type strong C var types to complement the flex var type of Jscript?)