The Proximity T-Shirt is a high end Proximity Device concept project. See that page for links to other related concept projects.

Over in our Google Group we started discussing a Proximity T-Shirt on Nov 14, 2009.

The basic idea is to have a t-shirt (or other wearable) that lights up and/or makes sounds when it gets close (in proximity) to another of its kind. 

Each object has the following minimums to accomplish:

     - See at least one other hacker at a time, with or without analog ranging.  

     - Signal the wearer / other hacker that the other hacker has been found

     - Be wearable with attendant size/power issues

     - ???

There are a couple variations on this that strongly impact the design:

• Individual IDs for items vs simply a Crasher-Shirt-Is-Here signal
• proximity is binary or a variable for distance (is-in-range, range-is-X)
• In a location where a central "server" could be called upon to manage the network

The simplest approach would only announce presence and detect another in-range. This would also be low cost and low power.  On the high end would have unique ids and have some sort of distance/signal strength inputs. The functionality will require more expensive devices in both cost and power measures.

Displays would be up to the individual, from simple beeps and flashing LEDs to music and LED array messages.

Sensing Technologies:

Passive RFID

Low cost and easy on the tag side, requires more power to stimulate tag and receive. Generally requires very close proximity, (<1meter) although higher power might get larger distances.

Active RFID

Devices such as the OpenBeacon could be used although the EUR pricing seems high. Alternatively SparkFun has RF Link transmitter and receiver modules that offer data rates up to 2400bps at about $5 each (xmit + rcv = $10).  SparkFun also has a number of boards using the Nordic nRF2401A transceivers. These are the same as used in the OpenBeacon project. Cost is about $20 each.

          RFID tutorial from RFID, Inc: http://www.rfidinc.com/tutorial.html

Zigbee/XBee

The Zigbee/802.15.4 is another alternative with a number of sparkFun boards. These are a bit higher cost ($10 for regulated board + $20-50 for rf module) and reportedly suck more power.

As a high-end device, this project is looking more at the Xbee devices.  The ability to support mesh networks is particularly interesting for even higher functionality devices.

First Steps:

1. breadboard a couple example devices, perhaps multiple approaches
2. find one that works reliably
3. document it for easy replication (pc board, etc)
4. make a bunch of em