I designed an accelerometer-based inclinometer for a piece of medical diagnostic equipment (non-portable) a couple of jobs ago.
The output of the accelerometer was an analog signal that was passed to an ADC. The output of the ADC was used to provide one of several indications of angle of inclination (as opposed to a digital readout of degrees). The ADC's data went to a Windows-based computer that was running the rest of the system, so we had sufficient data crunching capability to do whatever we needed with the inclination information.
There are uses in much equipment built today for an inclinometer or an accelerometer. Most cellphones and many other portable devices use accelerometers. As with my non-portable application, the output of the accelerometer needs additional processing. The output of a typical MEMS accelerometer is a voltage proportional to acceleration (g-forces) or tilt angle. So the next stage will be an ADC, followed by a microcontroller unit (MCU). Additional functionality will likely be needed for display aspects, but more on that later.
For applications like mine where all that's needed is a rough indication, this MCU-based subsystem gets pretty simple. If you want to indicate whether the apparatus was tilted too far forward or too far backward plus how close to vertical the system was, the MCU plus suitable firmware could easily drive a few LEDs from its output ports: 1-a ways to go; 2-almost there; 3-just right; 4-almost there (but the other way), etc.
In my application, I added provisions to automatically (well, mostly) do a calibration. The idea here is that you would move the apparatus to top dead center or vertical position. You would do this with the aid of a precision inclinometer that was accurate to within a fraction of a degree. Then, with a few keystrokes, the computer running the system would zero out the data from the accelerometer. As long as the accelerometer circuit board was mounted in its proper location, it would be close enough to vertical to start with.
Extending this design methodology to the MCU-based system is easy. Replace the keyboard plus computer with a pushbutton connected to a port bit (and a couple more lines of code). Tilt, push the button, and you're done.
If we combine the accelerometer with the MCU and add an LCD interface, we'd have a part that could be used in various portable (high production volume) pieces of equipment. Now, the LCD could show the same rough measurements as described above. Or it could provide a digital readout in degrees. Or it could indicate pictorially the position with respect to vertical.
Do you have a use for such a device? Can you think of variations on this that would be useful?