3 kinds of Glue for Ubicomp

Rajesh Jain blogs on Smart Mobs highlighting of an article on Anti-Mega:

It seems to me that there are primarily 3 kinds of glue, depending on where they get their information from, and what they transform it into. All 3 are important, and needed for ubicomp.

physical to digital glue ('inputs'):
CD ripper
DVD rippers
digital cameras
webcams

digital to physical glue ('outputs'):
Airport Express
PVRs
video senders

digital to digital glue:
web servers
APIs
UNIX-style pipes
wifi
3g

Physical to physical glue is mainly cabling, or dual deck cassette recorders, and gradually dying out.

The biggest piece of glue has to be the Internet substrata on which pretty much everything else relies. This has been ubiquitised by wifi and mobile phones.