This is a relatively simple project. The core component is either a USB keypad or a wireless USB keypad.
Then I figured out which leads on the numpad correspond to which numbers, soldered wires on the circuit board and connect them to the buttons on the remote.
You will also need a PC, a monitor and speakers. Any old PC or Mac will do, as long as it capable of playing video (about 450 mhz and above). Basically any computer that's 8 years old or younger will be able to do this. I used VLC to play the media files, but you can use an media player that allows you to change the shortcut keys.
I finished the whole project in about four hours.
Step 1: Parts Needed
I went with the wired remote, because anything not bolted down in my house has a tendency to end up somewhere where you wouldn't expect it. Lego blocks in the cup boards, lunch boxes in the bedroom, wooden spoons in the living room etc. If you have a toddler, you know what I mean. Not very practical to have a wireless video player remote in your front yard. I already had the numpad, but you can buy one from newegg.com for $10, or $30 for a wireless one.
Once you have your numpad, it's wise to first connect it to the computer and configure the player and test to see if you can actually control the player with the numpad.
In addition to the numpad I used the following computer parts:
An old Compaq M700 laptop. The laptop has a crappy battery and the lid keeps closing by itself. My wife used it, but she kept complaining that it was too slow.
I salvaged a 17" Philips monitor with build in speakers. When i found it, it was not working. I opened it up and found bulging capacitors. $2.30 in capacitors and 30 minutes later I had a monitor to use for this project.
On the electronics side, you will need some wire, a couple of buttons, solder and a soldering station.
This is where you have to decide how many buttons you want to implement.
I went with 5 buttons, play/pause, next and previous and fast forward and fast backward.
The buttons I used were ordered from Jameco:
315441- 2x Black Buttons
315432 - 3x Red Buttons