I tried but came to the conclusion that at least temporary root is necessary to install some files. The rSAP app itself will run without root access in the future.
I'm currently thinking of the following installation steps, which may replace the installer app:
- Connect phone to PC via USB
- The current kernel is extracted from phone and stored on PC
- An installation kernel is installed on phone. Now the phone restarts once to install the necessary files
- Original kernel is restored to the phone
- No permanent root, no Superuser app on the phone. This means more security
- Minimum changes to your phone
- The phone was temporarily rooted. I guess for warranty this makes no difference to a full root. I did not yet check if you have a yellow triangle on the Galaxy S II after this procedure, but the "flash count" will be increased.
- Bootloader must be unlocked for HTC and Nexus phones