I've seen people recommend putting printers behind a smart plug that can be turned on or off with a phone. Does this make sense power-wise? How much current does a printer in standby draw versus a typical smart plug like a WeMo?
This is really a matter of preference and opinion. In my opinion the amount of current being used is not significant enough to warrant turning them off for short periods of time (10 hours or less). It's always a good idea to shut everything down during long periods like when you're gone for the weekend or vacation.
In my opinion it's healthier to leave electronic equipment on since turning them off and on adds stress to the system. Think of an incandescent light. It burns out when changing state, usually off to on because the element is heating up and cooling off. It's not much different with electronic equipment.
By the way I own three printers a laser, an inkjet and a wide carriage and I really don't see appreciable utility usage.
All that being said, if you are traveling or for some reason you need to turn your stuff on/off from a remote location, it's certainly convenient to have the ability.
Hope this helps.