Determining proximity

1 . A method for determining proximity, the method comprising:

sending a wireless signal from a first mobile tag of a plurality of mobile tags, the wireless signal communicating identification information associated with the first mobile tag;

receiving the wireless signal at a second mobile tag of the plurality of mobile tags;

in response to receiving the wireless signal, storing proximity data comprising the identification information in a memory of the second mobile tag;

sending the proximity data from the second mobile tag to a mobile communication device using a first wireless protocol;

receiving the proximity data at the mobile communication device using the first wireless protocol;

storing the proximity data in a memory of the mobile communication device;

sending the proximity data from the mobile communication device to a server using a second wireless protocol, different from the first wireless protocol; and

storing the proximity data in a memory of the server.

2 . The method of claim 1 , wherein the wireless signal is a radio signal.

3 . The method of claim 1 , wherein the wireless signal is a Bluetooth™ advertising message.

4 . The method of claim 1 , wherein the first wireless protocol is a Bluetooth™ radio protocol and wherein the second wireless protocol is a WiFi™ or cellular radio protocol.

5 . The method of claim 1 , further comprising using the proximity data on the server to identify a set of the mobile tags that have been in proximity with a particular mobile tag during a time window.

6 . The method of claim 1 , further comprising:

determining that a user of the first mobile tag is a user of interest;

determining identification information associated with the first mobile tag;

identifying proximity data in the memory of the server that comprises the identification information; and

determining, from the proximity data, the identification information associated with one or more mobile tags that have received the wireless signal from the first tag.

7 . The method of claim 6 , further comprising:

identifying one or more users of the one of more mobile tags; and

sending a notification to each identified user.

8 . A system for determining proximity, the system comprising:

a plurality of mobile tags; and

a mobile communication device,

wherein each of the mobile tags is configured to:

send wireless signals communicating identification information associated with the mobile tag;

receive a wireless signal from another of the mobile tags, the wireless signal communicating identification information associated with the other mobile tag;

in response to receiving the wireless signal, store proximity data comprising the received identification information in a memory of the mobile tag; and

send the proximity data to the mobile communication device using a first wireless protocol, and wherein the mobile communication device is configured to:

receive the proximity data using the first wireless protocol;

store the proximity data in a memory of the mobile communication device; and

send the proximity data to a server using a second wireless protocol, different from the first wireless protocol.

9 . The system of claim 8 , further comprising the server.

10 . The system of claim 8 , wherein the mobile tags contain no long-range wireless interface and no wired network interface, and wherein the mobile tags are not able to send or receive Internet Protocol (IP) packets.

11 . The system of claim 8 , wherein each mobile tag is configured to determine a received signal strength indicator value for a wireless signal received from another of the mobile tags, and is configured to determine the proximity data from one or more determined received signal strength indicator values.

12 . The system of claim 8 , wherein each mobile tag is configured to calculate a range value as a harmonic mean of a plurality of values derived from a plurality of received signal strength indicator values when determining the proximity data.

13 . The system of claim 8 , wherein each mobile tag is configured to calculate an exposure value for another of the mobile tags, based on a plurality of wireless signals received from the other mobile tag over an interaction time window.

14 . The system of claim 13 , wherein each mobile tag is configured to calculate the exposure value by integrating, over time, a function of a plurality of range values derived from a plurality of received signal strength indicator values for the received wireless signals.

15 . The system of claim 14 , wherein the function is a Gaussian curve centered at zero range.

16 . The system of claim 8 , wherein the proximity data further comprises identification information associated with the mobile device tag that received the wireless signal.

17 . The system of claim 8 , further comprising a static beacon, the static beacon being configured to send wireless signals communicating identification information associated with the static beacon.

18 . The system of claim 17 , wherein each of the mobile tags is configured to:

receive a wireless signal from the static beacon communicating identification information associated with the static beacon;

in response to receiving the wireless signal, store static-beacon proximity data comprising the identification information associated with the static beacon in a memory of the mobile tag; and

send the static-beacon proximity data to the mobile communication device using the first wireless protocol.

19 . The system of claim 8 , further comprising a static gateway, the static gateway being configured to:

receive proximity data from a mobile tag using the first wireless protocol;

store the received proximity data in a memory of the static gateway; and

send the received proximity data to the server using the second wireless protocol, different from the first wireless protocol.

20 . A mobile tag for use in a system for determining proximity, the mobile tag being configured to:

send wireless signals communicating identification information associated with the mobile tag;

receive a wireless signal from a second mobile tag, the wireless signal communicating identification information associated with the second mobile tag;

in response to receiving the wireless signal, store proximity data comprising the received identification information in a memory of the mobile tag; and

send the proximity data to a mobile communication device using a first wireless protocol.