Health and usage monitoring of structures and active systems has received a wealth of attention in recent years. Microsystems are seen as a core technology for the realisation of these monitors as they offer the potential for multi-sensor integration with active electronics, wireless connectivity and in the future a self-powering capability. This article focuses on solutions for aircraft wiring systems where on-line detection of degradation and incipient failure would deliver improved safety and enhanced maintenance efficiency. Several approaches are presented to the problem of wire degradation detection in terms of both test and monitoring strategies. Both electric and mechanical (acoustic) methods will be presented together with simulation and experimental results.