^^^ If a dealership really wants to they can trace any remap while it's loaded to the car.
Only the superchips bluefin allows you to reflash the ECU back to stock and this takes a bit of time.
Both Revo and APR (via the select plus and cruise switch respectively) can be put into a stock mode which is just a way of reducing the performance to stock levels.
HTH 
I am not really sure how it works with Revo or Bluefin but I do know how it works with APR and I think what SteveP has listed is not perfectly correct.
We are the only company in the world that adds additional coding architecture to the ECU. This new coding allows the ecu to flash itself much like the dealerships, Bluefin and others flash the ecu's through the obd 2 port except it all happens internally.
ECU files are typically 2mb of total size including some marked and addressed but unused space. It is in these unused spaces that we insert our flashing coding and our operating maps or modes.
When you use your cruise control to select the mode you want, the ecu completely reflashes itself with a completely independent set of maps for that operating mode.
For example, going from 98 ron performance to stock requires the ecu to reflash itself with all of the operating maps that are different from your exact oem code. The 98 ron performance maps that are different than your oem code is then compressed like a .zip file and stored in the inactive memory locations until you use the cruise control to tell the ecu to reflash itself back with the performance maps. This means that other than the coding it takes to flash the ecu and the performance maps that are compressed and stored in an unused memory location, your ecu is 100% OEM operating maps and code. Not maps that we've inserted that have been detuned but completely stock mapping. In fact, the first part of installing an APR ecu upgrade with DPP is to extract your OEM performance mapping to be compressed and stored in the unused memory location. This means that not only are you getting an exact OEM stock mode, you are getting YOUR EXACT OEM STOCK MODE.
The performance mapping and flashing code that is stored in the unused memory locations is less than 2% of the total file and the total file size remains the same OEM 2mb.
It is technologically impossible at the dealership level to detect APR ecu modification as long as you are in stock mode and security lockout is turned on. The only way that the 2% of different coding can be detected is by Bosch Engineers or VAG calibration engineers that can completely extract the code on your ecu and compare it line by line to a version of the OEM code to find that 2% in difference. It takes alot of man hours and expertise to be able to do this and chances are you will never see this technology available at the dealership level.
Furthermore, some percentage of the Bluefin flash must not be OEM as well or you would be able to use you bluefin flasher on any ecu. The bluefin device must write a piece of code like a key or identifier in your ecu the first time it flashes it to know that the device belongs to that particular ecu. So, bluefin is less than 100% exact OEM code as well. Unless they write the code in the bluefin device which would make it very easy to unlock and use on every ecu you run across.
From what I understand by reading Revo's patent info, they do detune the performance map back to stock like behavior.
