Scanguage turns off check engine lights. It also reads the codes, and gives some realtime data which makes it better than cheap OBD scanners. For example, you can see your real water temp. On a D2, that can mean the difference between just replacing a thermostat or fan clutch, and replacing the whole engine. The factory gauge typically only moves after it's too late. But ONLY if you actually watch the thing. Saved me once already when I realized my rad was clogged with mud. I saw 215 and thought that isn't normal. Turn off the A/C, turn on the heat, windows down, get me back somewhere I can wash the rad.
It doesn't do anything with the SLABS system. That's what the ABS Amigo is for. It resets the lights, and stores the codes, but can only be read if you have a computer handy. The SLABS throws lights often for dubious reasons. Sometimes it's because of a pending problem, but it's totally reasonable to simply reset them, and continue your trip until you can address the problem properly. The ABS Amigo will not give you any real time data on the ABS system, or do a full ABS block bleed, however.
Neither of these will do anything with the Body Control Unit.