Summary
Lxfanalert is designed to watch a dodgy thinkpad fan and alert when it isn't operational. May or may not require options thinkpad_acpi fan_control=1 in modprobe configuration.
It polls /proc/acpi/ibm/fan every 15 seconds and detects failure based on the presence of a line like speed:.*65535.
License
Public domain - do whatever you want with the code.