How about a Hint lamp?
OldDudeInKyotoFu
REGISTERED
Game: fortythieves
Game #: 825764274
While I realize that Hint lamps are strictly for losers and wimps, Forty Thieves is quite challenging enough even with one to help the player out.
If it's difficult to implement, then go for a lite version, i.e. illuminate the lamp only and omit the highlighting of available move(s). This will at least let the user know that s/he might be about to miss a move - something that's easy to do in 40 Thieves.
If you don't like the wimp factor, make it a game setting to hide/display the Hint lamp.