Not exactly an "effect" but...

[MikeH]

has anyone thought about how to make a DIY ebow?  I've been working on a song that uses 2 ebows simulateously (which is rather cumbersome) and I thought it would be cool to create a contraption that vibrates all of the strings at once.  Like 6 ebows in 1.  Or perhaps an on/off for each one.

[petemoore]

  Yes, it's been done...
   'there is some info' is all I can offer.
  Passed for DIY 'effect' forum fodder ... I'd call it an 'effect'...'electromechanical and non stompbox'.

[Sir H C]

Fernandez has this that they put in some of their guitars.  Think they use the e-bow patented method.

[Arno van der Heijden]

Yes, this has been discussed here. Search the archives.