I use these:
on the rare occasions I smoke anything.
HOWEVER: in the spirit of this thread, I would honestly like people's opinions on these, because I should like to get my mom one - she's always talking about quitting, but usually only makes it a month.
If I can get her going on it, my dad is too much of a gadget nerd NOT to try one. Then again, he's a creature of habit, so who knows.
If I can get them to quit, a lot of the tension my wife feels about them being around our daughter will be gone (my wife, the rabid anti-smoker)