David Aspinall, Patrick Maier, Ian Stark Monitoring External Resources in Java MIDP ABSTRACT: We present a Java library for mobile phones which tracks and controls at runtime the use of potentially costly resources, such as premium rate text messages. This improves on the existing framework (MIDP - the Mobile Information Device Profile), where for example every text message must be authorised explicitly by the user as it is sent. Our resource management library supports richer protocols, like advance reservation and bulk messaging, while maintaining the security guarantee that attempted resource abuse is trapped. KEYWORDS: Runtime Monitoring, Resource Control, Java MIDP, Security.