Can I use an LED lighting power supply to power wifi devices?
A Constant Voltage LED power supply can be used as a DC power supply for non-LED loads. As with any power supply, there will some amount of noise on the output voltage. The WiFi units have their own internal power supply circuits to power the internal circuitry. 

Also note that the other type of LED power supply, the Constant Current LED power supply, is Not suitable to use as a DC power supply for non-LED loads.