e.g. ATtiny85, ATmega32u4.

We already began doing some stuff in this direction: publiclab/webjack#17

I managed to get the library sending on the ATtiny with Timer0. The problem with receiving is, that Timer0 uses the same pins as the analog comparator.

A solution could be the ADC multiplexer, which allows to replace AIN1 with an arbitrary ADC input pin. The downside of this solution is, that none of the other ADC pins can be used then, as the ADC has to be disabled.
It would be perfect if Timer1 can be used instead of Timer0. But I did not have the time yet to look closely at the differences between the timers.

For the ATmega32u4 the ADC definitively has to be switched off, otherwise it can only use the internal bandgap reference as negative comparator input.