Just enter a feed, filter a search term with full Boolean power, set how often you would like to be alerted, choose your method of delivery (SMS, IM, or email) and you are away…they also have a widget for your phone so you can go beyond SMS limitations.
People can tag feeds they are following and these are shared, so now you can discover feeds within ZapTXT, or even add the feed of the page you are on via the bookmarklet.
RSS to SMS, IM, and email are a big thing now, as there is so much information overload we are starting to segment our feeds…I know I want my essential reads shoved in my face via my GTalk IM.
At a glance the only difference I see compared to rasasa is a user directory compared to a house directory, archives your alerts, shows you which feeds (ZapTasks) are inactive, and the mobile widget.
Actually, rasasa also provides you with a spliced feed, and it allows OPML file import.