There's a very simple cure for neighbours or relatives who don't know when to leave ... flatulence.
simply position yourself between a source of air flow.. a slightly open window...possibly a heater vent..or a fan.. and the offending party... and eek one out quietly...
Then watch as they struggle to maintain composure and keep trying to talk whilst basking in the glory of the aromatic bouquet from your vindaloo you had but 2 hours before..
Although this falls into the crude-but-effective category..I've never seen it fail once

)
For added effect, you can follow the flatulence with some cute little saying.. .. something along the lines of 'There.. let's see the missus get THAT one out in a cold-water wash'.. or..'whoo baby, that one put on its' boots to come out and play'.. Very often if the actual flatulent event hasn't sent them on their way, the mental image you're imprinting in their little minds with the cute saying will.
Good luck... and remember the vindaloo.....
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Cycle related blog entries, including a few 5 minute reviews:
http://anotherdooratthe.endoftheinternet.org/category/cycling/