With the widespread deployment of Bluetooth Low Energy (BLE) enabled devices, we are moving towards a world full of distributed, resource-constrained devices. With this growth comes the challenge of maintaining and communicating with millions of intermittently connected low-power BLE devices. While sending data from these BLE devices back to central servers has successfully been realized at scale (e.g. Apple AirTags), downlink communication is more difficult. Given the common usage of BLE-only devices in public infrastructure and other safety-critical environments, this inability to communicate with devices in a timely manner poses a barrier to realizing safe and secure ubiquitous computing. We explore the design space of providing downlink connectivity to BLE-only devices, give an overview of the challenges, and propose a system to enable downlink BLE communication.

We demonstrate how to leverage Apple's Find My protocol, most well known as the underlying protocol of the AirTag, for arbitrary data-muling. This provides a new "infrastructure-free" deployment option, where areas with frequent human activity can take advantage of this zero-cost backhaul network. While there are severe limitations (e.g. no acknowledgement channel back to the sending device), Find My-based networking could still be a highly reliable backhaul with sufficient transmission redundancy and knowledge of deployment context.