Post-Dennard scaling CMOS technologies suffer from considerable degradation due to increasing electrical fields caused by the lack of further reduction of the supply voltage. This aspect of aging is widely disregarded so far and cannot be addressed at design time by adding static margins anymore. Instead, it needs to be counteracted effectively at run time over the entire device lifetime. For this purpose, dynamic runtime approaches for aging management are required, relying on detailed in formation regarding the current system state. In this paper we propose a novel aging monitoring mechanism providing that crucial information at a marginal resource overhead. The current device degradation is measured via the aging-dependent delay variation, which can be quantified in situ with built-in tests exploiting the strictly monotonic relation between supply voltage and propagation delay. Furthermore, we suggest to utilize the information gained this way for a proactive aging-aware task mapping.