I want to add a usb port to charge cellphones to my electronics unit?

Hello,

I am trying to figure out the best way to add a usb port to my e-nail unit. Here is a wiring diagram.

Two questions:

1.) Whats the actual electronic piece I need? I am no electronics expert nor am I majoring in engineering; but would something like this work? http://www.seeedstudio.com/depot/electronic-brick-5v-relay-module-digital-p-479.html

From what I understand, a phone charger would be connected to 5 volt usb port. So what is the best thing I could do to use the 120 volt circuit to power a 5 volt usb port?

2.) If you have a good usb port in mind I should use, how should I wire it based on my wiring diagram?

Thanks a bunch, and hope to learn more than a thing or two for you folks here!

 

Steve....would this work?

 

Aghh yes, let me elaborate a bit. So this unit is an electronic nail unit meaning its output it to a thermocouple heating coil which produces heat. A PID is a temperature controller. The part that says "no" is for the on/off switch. "no" stands for normally open. This is the switch: http://www.auberins.com/index.php?main_page=product_info&cPath=7_32&products_id=308

Thanks for your feedback...its hard even for me to explain and I build the things lol.

Red wires are hot terminals and blue wires are neutral.