Design & Develop Wearable Audible Alarm - Please Read Description In Full

We seek someone to design and develop a small wearable device that triggers an audible alarm once the item it is attached to is removed. For example a baseball cap. Person will attach a small wearable device to the adjustable strap at the back of the baseball cap. When the cap falls off the person's head, the buzzer alarm will go off. An accelerometer cannot be used since there may not be a lot of velocity once cap falls. The device needs to be able to sense that the baseball cap has fallen off, and battery should have enough power for at least a 30 day period and be easily replaced. Device will be used indoors so not subject to sun or heat. User should be able to adjust buzzer volume, turn it off and on, and see a small light indicating when battery needs replacing. Device cannot emit harmful energy as it will be near the users head. Person we hire must have experience to design the circuit and design the full enclosure. The enclosure strap must wrap around the back of the baseball cap strap and be adjustable to fit various widths. Materials used for strap will be either velcro wrapped in smooth felt, or silicone strap (like a watch strap) so it doesn't irritate the skin (bald heads) Finished prototype enclosure should be smallest and light as possible. Size should be smallest possible and no larger than the width of a standard plastic baseball cap strap. Smallest possible enclosure please. Battery choice depends on size and usage time. A small button cell battery OR rechargeable battery with docking station. Smallest possible battery is most important for 30+ day usage. Also important when choosing battery type is that it will be positioned close to the head so it must be safe. We will need BOM, circuit design, drawing, images, video of work, and 3 prototype units delivered to us for testing. First milestone will be paid at the time of shipping. Second milestone will be paid at the time of receipt and testing. Timeline - ASAP.