i thought computer fan motors were high speed, low torque?
i guess my concern is that when doing something like trying to dissolve a solid in a liquid, the solid which settles to the bottom would stop the stirrer, plus i don't know how you could use this design in conjunction with heating.
ive seen electric griddles (for instance by rival) which are temp controlled, (non-magnetic) aluminum, and the way they are designed there is plenty of room to put a stirrer underneath with very little distance seperating the magnets from the flask, but one would need a more heat proof design then the plastic computer fan.
lucky for me i got a great deal on 2 real magnetic stirring hotplates, literally i found on a curbside being thrown away in a not so great nieghborhood, so i can only imagine whAt they were used for in their previous life.