I've been using the LetMeKnow app - http://letmeknow.ws/ - to filter a city-wide transport information RSS feed and send me instant notifications of items mentioning certain terms that are relevant to my work. LetMeKnow has been discontinued, and whilst I can find loads of apps that push RSS feeds, I can't find any apps that allow me to receive push notifications of feed content filtered by keyword. Can anyone suggest a suitable alternative? I'm reluctant to use Yahoo! Pipes to do the filtering as the information is time-critical and I find Pipes feeds can be slow to update.