I bought tools from Walmart... and they didn't work. The problem is that the tools don't hold the HU well enough to pull it out. When you pull, the tools just slide out. Cheap ones may have more of this problem. I ended up shifting my HU over a little bit so the tools didn't even work on the left side. Thought I screwed myself and possibly broke something!
The solutions? Use your hands! NO TOOLS needed

The following steps work well.
1) take the glove box off by openning it, pushing in top edges inward so the rubber pieces aren't holding it, swivel it down and unclip the bottom left side, then slide it out toward the left.
2) take the plastic peice under the steering wheel off. You could probably just yank it off by pulling down from the top. It has 4 clips that hold it on the top that you could undo with your fingers one-by-one (I did this instead of the yanking). The top ones are hard to get with large fingers. It swivels down and you can unclip it from the bottom.
3) Pick one side (right is easier to get to) reach in by the front of the HU and push the metal plate down. It is spring loaded and holds the stereo in place. This is what the tools push against if done right when you pull the tools apart. Just push it with your fingers. While pushing down on the metal plate, push the HU out so the plate is not holding secure anymore on that side.
4) Now with one side out a little, go to the other side and do the same. Once you have pushed both sides out a little, you can just pull the HU out completely and disconnect the wires. It may be easier to go back and forth from side to side and get it slid out a little more before trying to pull the whole thing out.
Ta da! No tools, and only a minute or two!!!
Just for reference, I spend many frustrating hours with those stupid tools trying to get it out... I thought I broke something. I didn't realize what it was actually doing until I saw pictures online of a HU removal from a Miata. Retarded setup, but oh well.
Good luck!