sysmon —
system monitoring and power management interface
The machine-independent sysmon is a general purpose
  framework for system monitoring and power management. The main components of
  sysmon include:
  - An ioctl(2) interface
      available via /dev/sysmon. The userland
      counterparts include utilities such as
      envstat(8) and daemons such
      as powerd(8).
- An interface for the purpose of delivering different system and power
      events to userspace;
      sysmon_pswitch(9).
- A general purpose sensor framework,
      sysmon_envsys(9).
- A general purpose task queue,
      sysmon_taskq(9).
- An interface for watchdog timers.