To enable the concepts of smart cities, industrial monitoring, and precision agriculture, we are researching on lightweight, usable, and scalable security for wirelesss sensors and actuators. A recent result of this endeavour is the Adaptive Key Establishment Scheme (AKES), which establishes session keys for being used in 802.15.4 security. AKES supports mobile nodes, survives reboots, and is tunable from none to full compromise resilience. We implemented AKES as part of a new LLSEC driver for Contiki, a state-of-the-art operating system for IoT devices.