While great strides have been made in measuring energy consumption, these measures alone are not sufficient to enable effective energy management on battery-constrained mobile devices. What is urgently needed is a way to put energy consumption into context by measuring the value delivered by mobile apps. While difficult to compute, an accurate value measure would enable cross-app comparison, app improvement, energy inefficient app detection, and effective runtime energy allocation and prioritization. Our paper motivates the problem, describes requirements for a value measure, discusses and evaluates several possible inputs to such a measure, and presents results from a preliminary (unsuccessful) attempt to formulate one.