Are there additional motors and/or sensors that can be used to extend LEGO Boost?
I've tried attaching one of the Powered up motors from the batmobile set (76112) This motor looks identical to me as the WeDo motor (although brickset and bricklink don't list them as identical at the time of this writing) 

I could not get it to work, all profiles of the fixed build models complain that the external motor is not attached. The free build profile doesn't have any block that looks like the M-motor and using the boost motor block doesn't work either.

So my guess would be that at the time of this writing, no additional components are currently available for the Boost set...

The other way around, i.e. attaching the Boost motor to the hub from the batmobile, works...

I also purchased LEDs last saturday from an official lego store (had to ask, they had them in the back) they work on the batmobile hub, but I can't get them to work on the boost hub.