I was browsing around the web, stumble upon something that is new to me, data matrix.
more about data matrix here and here. Basically it is something like a bar code, that store info from a few byte to 2 kilo bytes. And is used as bar code, to identify object at a warehouse.
It seems that a few website, including nokia and this guy. Use it to encode data. It seems that nokia concept, is to encode the something, such as links or text. then expose it somewhere, then read it using a camera phone, with software of course.
Which I have my own.
it seems that there is reader provided in the links above.
There is other use of this as well, such.
Also there is a few library that can used to generate or decode the code.
http://barcode4j.krysalis.org/ (this is in java)
http://www.libdmtx.org/ (this is for linux, but unfortunately, it got sued by a patent troll, we we cannot download it)
which i should try to play around with it.