1-Wire™ is a system invented and implemented by Dallas Semiconductors and then bought by Maxim Semiconductors, the world-wide well-known innovative manufacturer of active electronic components.
In the 1-Wire family, the iButton™ components are very interesting. Physically they look very similar to wrist-watch batteries. Many different iButton models exist; all of them having interesting features:

• Each iButton has a unique on-board identifier: no two items with the same code exist in the world. This is very useful in applications such as electronic identity, security, traceabilty, etc.
  
  
• Most iButtons have an on-board write once (or write mostly) memory; the size can span from some tenths bytes to several megabytes. Memory can be used to store information that will be proprietary of “that specific ” iButton, identified by its unique code.
  
  
• Some iButtons have also the capabilty to measure temperature or humidity and to save data in a built-in memory that can be protected against unauthorized access.
  
  

Examples of applications: access control, industrial machinery activation, alarm control unit, frost and cold chain, environmental parameters logging. The sturdiness of these components make them very suitable for outdoor use even in case of large thermal changes, vibrations, shocks, drops, temporary dipping in liquids and oils.

RFId or 1-Wire?

All features of 1-Wire are available also in RFId technology; iButton is in effect an alternative choice. Which one technology is the right solution? This is the question.
There is no a unique answer; it depends on the application. Here are some suggestions:

As a matter of fact...	Therefore...	But, on the other side...
In RFId devices, technology is needed both in the transponder and in the reader. In iButton devices, technology is only in the transponder: the reader is just a simple couple of wires	1-wire reader cost can be much lower than a RFId reader	The cost of iButton (even a low-end model, code only) is much higher than a conventional RFId tag
RFId reader is wireless, while 1-wire needs electrical and physical contact between tag and reader	RFid is more flexible because it can be read even behind an obstacle (e.g. in a box or in a pocket)	1-wire electro-magnetic noise immunity is practically total; therefore it is ideal for industrial applications even in severe environments (e.g. heavy industries, electrical power plants, ...)
iButton is extremely sturdy, thanks to its hermetically sealed steel case	Generally speaking, iButton can withstand harsh environment, where most RFId tag can’t	Sturdiness costs: if our application don’t need it, may be you are wasting your money
1-Wire is a mature technology, while RFId is still strongly evolving and attracting many capitals	In general, RFId rather than iButton could be a better choice for a new project	Mature technologies are more stable and tested: in critical applications this can be a premium. Moreover, Maxim guarantees to support iButton at least until year 2012: there is enough time to take advantage of the device excellent features even in new projects