Though in my opinion related to the topic, these devices are not much covered in this text, yet. For general information about Embedded Systems, see http://www.embedded.com . For Linux information, see ELKS http://www.elks.ecs.soton.ac.uk/ and the uCLinux project at http://ryeham.ee.ryerson.ca/uClinux . See also news:comp.arch.embedded
Also related to this topic but not covered yet seems wearable computing, see http://lcs.www.media.mit.edu/projects/wearables/ and the page of Lionel, "trollhunter" Bouchpan-Lerust-Juery, http://infonomade.linuxfr.org/indexen.html for further information. http://wearables.blu.org
The datalink library allows sending information to the Timex DataLink watches. The original datalink library supports the model 150 and possibly the model 70 watch. This version has been extended to work with the DataLink Ironman Triathlon watch. It has been tested with the SVGA output on the Ironman watch only, other output devices and other watches may or may not work, I have no reports either way. The display must be a CRT display (not a LCD).
For NOKIA cellular phones see GNOKII project . And Linux Nserver. This project aim is to produce a GPL replacement for Nokia's Windows Nserver, and maybe improve upon it along the way. Initially it will emulate the Windows 3.1 version (ie. allow backup, restore and install).
SMS Client is a UNIX command line based utility which allows you to send SMS messages to mobile phones and pagers. This software has been written and tested on Linux however a number of users have reported success running under both AIX and Solaris. SMS Client currently supports a wide variety of services providers and protocols.
For information about cellular phones and digital cameras see some links at my page about Linux with Infrared Devices and my IR-HOWTO.
Information about calculators e.g. HP48 is at HP-Calculator.Org and Keith's HP48 Page. See also at my page about Linux with Infrared Devices.