ipmi —
Intelligent Platform Management Interface driver
The ipmi device driver supports motherboards
  implementing the Intelligent Platform Management Interface version 1.5 or 2.0,
  and exports sensors and the watchdog through the
  envsys(4) interface.
The ipmi driver is able to send events to
  powerd(8) when a sensor's state
  has changed. Intrusion sensors will send a critical event
  when state is not ok. Power Supply sensors will send a
  critical event when the Power Supply unit is not installed
  and warning-over when the Power Supply unit is installed but
  not powered on. Fan, temperature and voltage sensors will send
  critical-over or critical-under when the
  value is very critical, or warning-over or
  warning-under if it's in a warning alert.
The ipmi driver first appeared in
  OpenBSD 3.9 and was then ported to
  NetBSD 4.0.
The ipmi driver was originally written by
  Jordan Hargrave and was ported to
  NetBSD by Manuel Bouyer
  ⟨bouyer@NetBSD.org⟩.