Clap detection (or any other loud sound?)

We'd really need to know just how much voltage you get from the microphone when there's a clap before we know if it can be connected directly. @allObjects solution looks great if you can't connect direct though.

You could keep checking the analog value, but that's going to use a whole bunch of power - so using a battery won't then be a very viable option.

Bluetooth Espruinos do have a 'low power comparator' which can work to 1/16th of the supply voltage (or can compare to the voltage on pins D2 or D3): http://www.espruino.com/NRF52LL

So you could set that up - although the current solution in Espruino will require you to use two pins connected together so that you can then use setWatch to trigger code to run when the voltage goes above a certain level.