Texas, I did not mention Bosch because .... Bosch North America has made a deliberate decision to NOT import these tools for this market.
Found that out when I tried to buy one ...
Hotline ... what these tools do is make a pair of saw cuts about an inch apart. You still need to chip out whatever is between the slits, though a lot of the material just falls away.
Oops... didn't know about Bosch! Sorry!
This tool is basically a dual-blade circular saw with diamond blades that will cut plaster, stucco, brick and to some extent concrete. Most ECs then use a Hilti or other electric rotary hammer to chip out everything else. To some extent you can also use the plaster groover to cut in boxes, at least for the vertical cuts on a single gang or all cuts for larger boxes. For wall light boxes you could switch to core drilling... on the other hand a core drilling bit that size would most likely be impossible to use free-hand. In countries that use 60mm round switch boxes, 83mm diamond tipped core drilling bits are fairly common for installing boxes, they speed up the process considerably and reduce damage to the wall - just chiseling will give rather jagged holes and in old buildings might cause a LOT of plaster to fall. Here in Vienna, pre-WWI plaster usually didn't have any lime or cement content at all, it only consists of mud (clay/adobe), often with a cement based finish coat. That stuff chips off like crazy!
Oh, and anyway, try to convince the home owner, that plaster repair isn't black magic, at least if they're DIY types! Finding a good plasterer in the US might be a little hard...
