I know it is possible to subscribe to keywords searches by saving them within Twitter's app as a saved search. There doesn't seem to be a way to get notified by email of these searches nor scope the searches to my followers or followees, e.g. An RSS feed or daily email
If this isn't possible, us there any service that would alert me when a follower or followee mentions a keyword? I realise there are services like monitter and twinitor which monitor keywords, but none on the basis of an individual account.