Reflections: 

What really helped me is thinking backward and starting with problems, rather than seeing what sensors are available and figuring what to do with them. When you think of trying to solve the problem rather than connecting all the sensors to function, the solutions will actually be useful to the client. 

From my case, I believe that this little prototype can actually solve the problem elegantly, adding a few tweaks. I showed it to my mom via video, and she liked it a lot. The concern is that it should not be the only mechanism that completely replaces the previous one. There should be a double mechanism that acts as fail-safe in case there are malfunctions. She would also want to get information on her phone of the status of the system while away. This can be implemented with deeper incorporation with IFTTT.