  Enabling direct communication between wireless technologies immediately
brings significant benefits including, but not limited to, cross-technology
interference mitigation and context-aware smart operation. To explore the
opportunities, we propose FreeBee -- a novel cross-technology communication
technique for direct unicast as well as cross-technology/channel broadcast
among three popular technologies of WiFi, ZigBee, and Bluetooth. The key
concept of FreeBee is to modulate symbol messages by shifting the timings of
periodic beacon frames already mandatory for diverse wireless standards. This
keeps our design generically applicable across technologies and avoids
additional bandwidth consumption (i.e., does not incur extra traffic), allowing
continuous broadcast to safely reach mobile and/or duty-cycled devices. A new
\emph{interval multiplexing} technique is proposed to enable concurrent
bro\-adcasts from multiple senders or boost the transmission rate of a single
sender. Theoretical and experimental exploration reveals that FreeBee offers a
reliable symbol delivery under a second and supports mobility of 30mph and low
duty-cycle operations of under 5%.
