I haven't, but have thought of some ways to do it. Hate to get rid of my factory radio because I like it better than double dins. I believe some GPS units have back-up cam capability via bluetooth, another option if you don't want to dump your radio. Just think of the am/fm in the 72s... back then nobody thought it would be a bad idea to upgrade to a Kraco with am/fm+CASSETTE!!
But - double din probably the slickest way to go for built-in approach. I added a lower end model dash cupholder to my silverado (yes, now have 4 cupholders, but it looks factory correct
) and have been toying with some idea on how to hide a GPS inside the fold-out cupholder and use it as GPS/bu cam only, when it is open. But it's a pretty tight fit, kinda gave up and decided to get 4 big gulps. But it is a starting point...