On a recent roadtrip, I did some "wardriving" where you scan for 802.11 (wifi) access points. Today they are everywhere. The scanning program lists the network name (SSID) as well as other information like the model of access point and whether it has encryption on. Often the SSIDs are informative, with the names of families and companies. Mine is an web address that would let a neighbour contact me.
All this happens because most access points transmit a regular "beacon" packet which lists their SSID and other information needed to connect to them. Seeing that the SSIDs were sometimes interesting, I wondered if we might do much more with a special beacon.
This beacon would deliberately tell you a bit about the access or location. It would contain a mixed XML/HTML packet with a variety of useful fields and general text. These could range from simple descriptions ("This access point belongs to Joe Smith, I'm a programmer") to information ("On this site, Paul Revere stopped on his ride to consult with local minutemen") to street directions ("Turn right to get to highway 101, left for downtown") to, of course, advertising ("We sell fresh fruit and have a special on plums today.")
In other words, a replacement for signs and billboards and markers. And perhaps much more. Access points would also talk about themselves, declaring, for example, if the owner is offering open internet access for free or for fee, or has a local database of information, and what classes of information are in the main text. The local lattitude and longitude for those without a GPS could be useful, along with local map data in a compact form.
Users could quickly get a program for their laptop (such as Netstumbler) to read and display such virtual annotations to the world as they drive. Primarily for passengers to use, of course. Eventually dedicated boxes would become available, and onboard car computers and GPS units could understand the protocol. Mass market access points would include a set-up screen in their web interface to let the owner enter the information beacon text and enable it. (Today some APs have open source firmware and an energetic programmer could do this right away.)
All of this might be both useful and entertaining. Children might enjoy reading all the random bits of information that flow by and stop asking "are we there yet?" The journey can become the reward. (Of course remember to look out the window sometimes.)
I can imagine vendors making a cheap solar powered access point that, during the day at least, sends out information beacons as soon as enough power is stored in the capacitors to send one. These could operate on a small, cheap solar cell (the more power, the more frequent the beacon) and be placed anywhere. "I'm an oak tree!"
Below, I will get into some technical issues and discuss the unanswered question, which is how to avoid abuse by excessive advertisement, spam and falsehoods.