We were severely warned off it in our NCT class. Basically it works on the principle that it will irritate your bowels to the extent that it could stimulate contractions. However for most women they just end up with violent diarrhoea and feeling really miserable. Even if it stimulates a few contractions, it often doesn't result in effective labour. Also, even if you did go into labour as a result, talk about uncomfortable - having to deal with contractions as well as rushing to the toilet every two minutes. If you have diarrhoea you'll also probably be dehydrated - basically not recommended. Besides a really hot curry should stimulate the bowels and probably would lead to the same outcome - it will work for you if your body's ready to go into labour but if it's not, then it's most likely to just give you an upset stomach.
However I've never tried it myself, and who knows what I'll try when I get desperate - I really don't want to go overdue!!
Good luck
LBxx