This is also built into ICS leaks for Bionic. If your on ICS and boot into recovery it will show if you ever have been or currently are Rooted.
What I do know is that even FXZing to .905 and back to a ICS build won't reset it. Again, just provided for everyone's information.
"qe 0/0″ means your device has never been rooted
“qe 1/1″ means your device is currently rooted
“qe 0/1″ means it was rooted before, but currently isn’t
See link below for more info
Root checker found in DROID 4 and DROID RAZR/MAXX Ice Cream Sandwich builds