Outcome

The final product works as intended, though admittedly the package is a bit unwieldily.  It can easily be attached to a doorknob using rubber bands or adhesive, but the bulky breadboard prevents easy operation of the knob itself.  The power source (USB cable or battery pack) doesn't help either.  It really requires a more elegant enclosure.

While encasing the device is a longer-term goal, a more immediate improvement would be the addition of better notification services.  The cloud logs are nice, but SMS alerts would be much more noticeable.  One more thing to look at is idle power consumption.  Ideally, the circuit should be extremely lean, and I have not tested this aspect of performance yet.

Reflection

This project was highly informative for me, and a great hands-on learning experience.  I work closely with several electronics engineers on a daily basis, and I am consistently baffled by the complexity of their work.  Building this device gives me an even greater respect for what they can do.  That said, I felt that I achieved the goal I set out to reach (even if I did receive considerable assistance), and now feel inspired to continue developing more advanced devices.  I'll be pressing on with a new, but appropriately restrained sense of optimism.