A while ago I bought an AIM Solo DL. It does a great job of logging data from the car's ECU and displaying predicated lap-time. It's not as handy as a full size racing dash, but it's half the cost. One of the nice feature about the SoloDL is that you can program pages to display channels from the ECU like engine temp, fuel level, etc. or from the onboard sensors (Accelerometers, GPS Speed, etc.). I wanted to be able to flip through the pages without reaching up (and in my case) through the steering wheel to press the buttons on the front of the unit.
So, I pulled the unit apart to take a peek inside. It comes apart very easily, just beware that the battery is mounted to the rear case lid and needs to be unplugged when you split the case.
There is no need to further disassemble the unit, but for reference there is a small board behind the main board that is populated with the buttons and connected via the 5 pin header to the main board. These 5 pins are common plus the 4 buttons on the front of the unit.
Solder the wires onto the pads here (first use a meter to find the common pin and then the pin for the button you want to use (I used the "right most button" for paging through the screens).
Simply drill a small hole in the side of the case and run a pair of wires through, strain relief them on both sides with a small ziptie or something similar and a dab of RTV for weather protection.
On the external side, i pinned the connectors to a Weatherpack 4 pin plug, so that i could easily disconnect the Solo from the car.
Obviously, this will violate the warranty!