SMSs can be concatenated to form bigger SMSs. I routinely send SMS messages of more than 140 characters, but am obviously charged for multiple SMS messages in that case. However, neither the sender nor recipient notice this aside from a small counter in the top-hand corner of my Nokia phone which says how many SMS messages it takes to carry it.

Twitter's 140 char limit is fairly arbitrary, as evidenced by the likes of Brightkite, Facebook and other ublogging services.

Yes, correct. Some of the passports out there already provide ATR randomization providing random anticollision IDs for each query, so there's no unique data which can be used to identify the passport.

Unfortunately this is not widely used yet, though in all honesty, following your cell phone IMEI or Bluetooth code is far easier than trying to read the passport anticol id - you need a really large and expensive infrastructure in order to have any sort of massive tracking capability for this near field RFID...

Or just buy one of the Nokia phones which already have an RFID/NFC reader in them (yes, it can read passports).

http://europe.nokia.com/A4991361

There are multiple technologies, all called RFID. Some of them have very short range (like the ISO 14443 used in the passports, also known as NFC), which has pretty much a maximum distance of one metre (due to the coupling it uses).

However, there are other technologies which allow far longer reading range - such as the one used in these inconveniently named "passport cards". The EZPass cards can be read from the range of several metres fairly easily.

Don't confuse these "far field" and "near field" RFID technologies. They are physically quite different beasts.

There is no need for a self-respecting geek to wait for others to get their stuff together. These phones (e.g. Nokia 6131nfc and 6212) have an RFID reader AND writer as well as a programmable platform (Java MIDP) and cell connectivity in a single package.

So a shop owner could create his own loyalty card system (just read the Oyster card's ID and put it in a database) or make up a game of geotagging.

Why bother to wait for the payment stuff? It's cool as it is. :-)

Yeah, I'm biased, having worked in the area for quite a while. But there's no need to wait - just get the phones and hack away :-)

Nokia 6131nfc and Nokia 6212 already contain the necessary hardware. Both are on market, the former has been around for over a year. They are not carried by any US operators, but they are available in some European countries, like Austria.

Check out http://europe.nokia.com/A41197323?&loc=use_nfc or search Youtube for "Near Field Communications".

Oyster phones (=the Nokia phone with an Oyster card on board) also exist in the UK, but still in pilot usage.