There’s also Autoremesher, a stand-alone open source auto-retopologizer:
Haven’t tried it myself, so I don’t know how it performs on hard-surface models.
One thing I know for sure, being familiar with all solutions mentioned so far: Quad Remesher is the king of auto-retopology in Blender, and it can usually handle hard-surface models quite well.
If you frequently work for clients from the CAD world who are used to the price tag of a tool like Solidworks, I don’t think Quad Remesher is an expensive investment at all.
You can read all about Quad Remesher in this thread: