This is just a quick listing of the tests that each IFO has in their DIAG_MAIN Guardians and their docstrings.

LHO

ALS: ALS checks, This can be seen when the beatnote drops down to 0-2 MHz and when (in dBm) it gets above 5. Checks to see if the ALS SHG Temperature Control Servo is on Nominal is 'ON'
BEAM_DIVERTERS: The Beam divereters should be closed after the ISC_LOCK state of CLOSE_BEAM_DIVERTERS #550. 1 == closed, 0 == open.
BECKHOFF: Beckhoff status check
Check some random Beckhoff channels to see if the system in running.
COIL_DRIVERS: Coil drivers functioning, If they stay at 0, it will bring up a notification
ESD_DRIVER: ESD driver status
HWS_SLEDS: HWS SLEDS are on
HW_INJ: Hardware injections running
ISI_RINGUP: ISI ring up motion as seen in alog24245, Only looking at the ETMs and non rotational dofs for now.
MC_WFS: MC WFS are engaged
OMC_PZT: The OMC PZT2 high voltage should be on, otherwise the OMC_LOCK Guardian will fail at the FIND_CARRIER step
OPLEV_SUMS: Optical lever sums nominal, Check only when the suspension is aligned.
PEM_CHANGE: Major environmental changes
PMV_HV: PMC high voltage is nominally around 4V, power glitches and other various issues can shut it off.
PSL_FSS: PSL FSS not oscillating
PSL_ISS: ISS diffracted power
PSL_NOISE_EATER: PSL noise eater engaged
RING_HEATERS: End station ring heaters on
SEI_STATE: SEI systems nominal, Also checks if the WD saturation counts are are greater than somepercent of the limit.
SEI_WD: SEI watchdog not tripped
SERVO_BOARDS: These are Beckhoff controlled channels and cannot be monitored by SDF yet.
SHUTTERS: Monitor the Beckhoff controlled shutters
SUS_PUM_WD: RMS watchdogs
SUS_WD: SUS watchdogs and OSEM input filter inmon on the quads
TCS_LASER: TCS laser OK, Switched ON, Power above 50W, No Flow Alarm, No IR alarm, Only for TCS X for now.
TIDAL_LIMITS: Tidal limits within range

LLO

ALS_LASER: ALS laser power above threshold
ALS_PLL: None
ALS_SERVO_POLARITY: ALS servo polarity monitors
BECKHOFF: BECKHOFF system monitor
BSOPLEV: Beamsplitter OpLev Monitor
IOP_DACKILL_MON: Monitors IOP DACKILL status and reporting faults
ISS_DIFFRACTED_POWER: ISS Diffracted Power monitor
OMC_PZT_HV: OMC PZT HV monitor
PARAMETRIC_INSTABILITY: PI not rung up
PRC_GAIN: PRC gain above threshold
SEI_ISI_T240_SATMON: SEI ISI T240 saturation monitors
SUS_QUAD_ESD_BMON: QUAD BIO ESD driver digital monitors
SUS_QUAD_ESD_DMON: QUAD ESD driver digital monitors
SUS_QUAD_L3_BIO_CHECK: QUAD L3 BIO switch consistency check
SUS_QUAD_PUM_WD: QUAD PUM RMS watchdog   
static_vars: None
 

To get these I opened a python shell and imported inspect and the desired module, then...

for name, obj in inspect.gemembers(module_name):

    if inspect.isfunction(obj):

        print '{}: {}'.format(name, inspect.getdoc(obj))