Well, this is not actually a hack, it is just a trick. Here's the main screen:
If you tap the upper right Battery Icon for 5 seconds this interesting menu will pop up:
Here you have a secret diagnostics page. You can test ROM, RAM, monitor temperature levels, USB cable detections, battery level, etc...Press next and you have further options:
I Pressed Start Test, but it's a background test, does not show you anything else other than the results show at this page. Here you have an interesting "More" button that shows you info on your current Garmin Software Inventory. It's interesting to see how some were removed:
You can even test for dead sub-pixels. I found out i had a dead sub-pixel on the lower right corner. But completely unnoticeable otherwise.
Here you can test the current voice you have set on your GPS among other things: