"I want photos of birds at my feeder sent to my phone." A tiny camera board next to the feeder takes a photo when something moves and sends it to your phone. It's cheap and fun; the photos are decent, not wildlife-magazine sharp. Cost $15–30 · Time...

"How do I get warned before a leak under the sink floods the kitchen?" Water conducts a little electricity. Two metal contacts a few millimetres apart on the cupboard floor, a small board that checks them, a loud buzzer and a phone alert. The test i...