I used to work on aircraft engines (Radials, opposed as well as turbine). They had mag plugs, as they were called. They weren't used to clean the oil, though, they were used to let us know when to change the engine. In order for a particle to be attracted to a magnet, the particle must pass through magnetic flux sufficient to attract it. Given the fact that the oil is flowing, the magnetic force must have the strength (or proximity) to pull that particle against the current, so to speak. A little ole' oil plug just isn't designed for that, but one of the supporters of this forum makes a product that is. Bossproducts.us makes a variety of magnetic filtration systems. check their site, there are some real big research papers there as well, for the technically minded, that is ;-)

excitedVulcan

 

The magnetic plug is a good idea.
There is little movement of oil
on the bottom/side of the oil pan, and virtually
no movement in the front pan sump.
Any particles will easilly be attracted to the
magnet.
Inspecting the magnet every oil change
is probably a good idea. But there is not
much you can do when you start to see particles.