My suggestion is based on that only you really know what to do but maybe we can help you find it. Begin with you daily life and solve a problem.
For example:
Do you need to water the flowers? Make it automatic with online ui.
Do you always need to check if your door is really locked? Make a lock status report system.
Do you missing people trying to ring the bell at your house because you are in the garage? Make a camera which sends a mms with a picture of who is infront of the door.
Solve something you want to be solved!