Early GSM handsets provided a single function: voice communication across a bi-directional link of 10kb/s. High-end mobile phones supports multiple radio standards and a rich suite of applications, which involves advanced radio, audio, video, and graphics processing. The overall digital workload amounts to nearly 100GOPS, from 4b integer to 24b floating-point operations. With a power budget of only 1W this inevitably leads to heterogeneous multi-core architectures with aggressive power management. The authors review the state-of-the-art as well as trends.