auto-cpufreq is a new automatic CPU speed and power optimization tool for Linux laptops using Intel CPUs, which aims to "improve battery life without making any compromises".
The tool changes the CPU frequency scaling, governor (switches between performance and powersave, these being the only 2 modes supported by the default intel_pstate scaling driver) and turbo boost status based on the battery state, CPU usage and system load. It can also show some basic system information, monitor the CPU frequency and temperature for each core, system load, and battery state.