Useful Wi-Fi extension: add user-programmable field for access points

I was doing a little research into Wi-Fi positioning systems (like Skyhook), and it occurred to me we're missing out on huge opportunities in the Wi-Fi space. Skyhook can tell you within excellent resolution where you are, based on a combination of an extensive access point address to physical location database and signal strength information (now even assisted by GPS and cellular radio).

But there's another way to look at this problem, which would give a more democratized and rich solution, however with attendant noise and error. Many access points (APs) are programmed to send out periodic "beacon" packets (unless programmed not to announce their networks). These packets are designed to allow devices to discover Wi-Fi networks before attaching to them, so no transmit capabilities are needed to receive them. Why not allow an extension of the IEEE 802.11 protocols such that a given AP can introduce a programmable payload of data into an extended field in the beacon (or other such) packet? GPS coordinates would be an obvious payload component.

While researching this, I came across interesting suggestions to use XML to encapsulate the data. Of course, packet length is important, so either payloads would have to be short, or perhaps have critical fields (GPS coordinates for example) and a reference URL to the rest online. There are many possible useful bits of info which could be in the XML payload, such as those in one related suggestion:
Perhaps they could also provide hints such as, "quiet area: devices should switch to vibrate mode here."
In any case, what I like about offering user configurable data is that the packet fields only need to be extended once and the XML format can evolve independently. And perhaps as importantly, devices can glean information without having to ever transmit information. Receive-only or lower power devices could use this data, opening up a whole new world of opportunity! Maybe we'll see a pair of shoes which gather a whole stream of information as we walk about cities, all self powered by our walking...

Disclosure: no positions