Do aircraft have accelerometers? Do modern aircraft employ accelerometers or other similar equipment to measure g-forces on the aircraft? I could imagine this being used as an inspection/service indicator, particularly after hard landings. Or do hard landings and other forceful flight regimes typically not pose any significant structural concerns?

Update. Related on determining hard landing inspections:

From Aero Magazine on Boeing conditional inspections

Section on AMM changes:


  Boeing is modifying the 737 AMM, section 05-51, and will revise the AMMs for other Boeing-designed airplane models, to include these vertical acceleration values (table 1). For Douglas-designed airplanes, similar values are being generated and will be available in the AMMs in early 2001. The values are intended as thresholds that can be used to help determine whether a hard landing inspection is necessary. If the flight crew concludes that it has experienced a hard landing, the AMM conditional inspections should be performed even if the acceleration readings do not exceed the values added to the AMM. The vertical acceleration values are to be used by operators, in addition to or in lieu of flight crew judgment, to initiate conditional maintenance inspections.




Source: Aero Magazine
Most modern aircraft, which includes long range airliners since around 1970, all airliners since not much later, and basically anything with glass cockpit, do have very accurate accelerometers for all three axis, as part of the inertial reference system. 

They are important instruments for the autopilot, as they provide faster feedback on the effect of control deflections than the air-data references, and essential for navigation as cross-reference for detecting GPS errors and the inertial navigation serves as a backup for GPS (and served as primary navigation over the oceans before wide GPS availability). Airbus (since A320) even defines the pitch command by vertical acceleration in the normal law. And yes, they are also used for detecting hard landings and their severity.

The pilot never sees the direct accelerometer output except in fighter and aerobatic aircraft though (well, almost never; there are a couple of other cases).