Our half-bathroom has no power outlets beyond the one in the base of the light fixture above the medicine cabinet. I’m fairly sure that code prohibits such outlets so close to a water source, and since we’ll be replacing that light fixture in any case, it’s unlikely the replacement will provide a similar feature. I hoped to expand the current light switch enclosure to hold both an outlet and switch, but–given (1) my lack of any wiring skills and (2) the walls of solid concrete–I worried that such a task would be beyond me.
Home Depot supplied the hardware that would encourage me to try anyway: a combination light switch and GFCI outlet, made to fit in the space normally taken up by just one switch or outlet. The wiring proved a significant test for my amateur skills, so after trying a few permutations (that resulted in different–but all wrong–combinations of the outlet and switch working), I finally found this diagram that clarified things:
A cool little outlet-tester confirmed that everything was working.