Losing your bike is not fun, but it could happen to anyone. This Smartphone Alerting Bike Alarm connects your bike to your phone, allowing you to keep track of it and get an alert when your bike is moved. It has a built-in motion sensor and connects to your smartphone via Bluetooth. It has a range of 295′. The device looks like a regular bike light and attaches to the seat post. You can turn the light at night to stay visible in the dark. Sets you back under $100 at this time.