if you exclude credit cards and id tags (for which there would be hundred of millions of examples),
the most popular tag types are those that support ndef. ndef is a level of abstraction capable of
supporting many tag types which recognize it. think of ndef as b4x; you code in b4x, and your app
can run on windows, linux, iphone, android and tiny systems. tags may come with support for its
native type (A,B,E,V, F) as well as for ndef. phones with an nfc chip usually offer good support for
an ndef-formatted tag out of the box. these other types may be recognized by phones, but coding
to those standards is not always trivial. the differences in these other types usually relates to
improvements in speed and signal strength. eg type F is faster than type A. also more expensive.
credit cards and id tags don't use ndef, so, although android can recognize the card, you
have to write a lot more code than is required to read/write an ndef tag. and in some cases,
documentation and access to security keys may require a lot more (time and money) than
you care to spend. and even then, the provider may not want to deal with you. and even if you know
how to access certain data relating to credit cards, the actual data may not be kept on the card.)
the type of tag used depends on its function. slower tags with smaller memory are very cheap for
small tasks. faster tags with more memory and encryption are more expensive and are used for
more complex tasks (eg, transport passes).
the most popular tags are manufactured by a german company nxp. they produce the mifare
line as well as a line of so-called 2xx chips (eg, 203, 212, 215, etc). if you scan through the tags
offered on ebay, you'll see all of this. you can get an idea of how much they cost. memory sizes
usually go from 64bytes to 8K. they sell in packs of 10, 20, etc, and in a variety of sizes. i am the
proud owner of a large personal collection, including several rare specimens from japan. i maintain
a small museum in my basement. visitors can hold their android phones over the exhibits and read
inspiring ndef messages written by me.
