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’):
digital to physical glue (‘outputs’):
digital to digital glue:
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.