Replacing two pronged outlet with GFCI not grounded...is it adequate for electronic devices?
You can get a 3-prong plugin at locations that only have  2 wires by installing a GFCI.  There should be a label in the box with the GFCI that says "No Equipment Ground" which must be applied to the face of all 3-prong outlets protected by the GFCI including those downstream.

It's perfectly safe for your power tools, plug your drill, etc in as much as you want.

A surge suppressor plugged in at that location will NOT work. The wiring fault light on the unit will be on, because the is no actual ground which it need to suppress a surge.

Your smart phone probably isn't 3-prong. 

Edit: (thanks to @craig in comments) Laptops with a ground pin should not be used in a GFCI labeled as "No Equipment Ground".  There are varieties that may need Equipment Ground for effective static discharge. I can also find examples where I don't believe that's the case, but it's better to say laptops should not omit the equipment ground.

"Other" electronics may vary by what and why it's a 3 prong plug. The consideration is that the human safety from electric shock is covered by the GFCI, if however the device needs ground to dissipate static charge, or has built in surge suppression, it should not be used in an outlet marked "No Equipment Ground".