This can also be used to power a router, switch, access point or hub that is located in a area that does not have power. For example, you may want to use this method to relocate a WiFi access point to the attic or in a drop ceiling at the office.
The Commercial Linksys POE power injector adapters go for around $40. Power injector adapter
I had the materials on hand which is what prompted me to do this project. You should be able to pick up the materials for under $8...given that you already have a spare Ethernet cable lying around.
2 - RJ45 Ethernet (cat5) wall plate jacks.
1 - RJ45 Ethernet (cat5) patch cable.