Dutch telephone store Primafoon (primafoon.nl) does one better: It sells (aside from iMacs and iBooks) this little gizmo:
The miniphone. It comes in orange, purple and blue, is translucent, sports two standard RJ11 phonejacks, adjustable (speaker) volume, redial option, flash button, red ringer-light, green in use light, a headset consisting of in ear phone with mike on bendable wire, great quality sound. It comes complete with RJ11 to wall socket cable and neck carrying cord.
Now if they only supplied the Velcro tape in matching colors (you'll have to find your own Velcro tape to attach it to the side of your iMac, which color it perfectly matches)
To find it, point your browser to www.primafoon.nl. click on "Telefoon Thuis", click on "Telefoons en apparatuur" , click on "Gedrade Telefoons"
You'll find it there for the price of 49 guilders, about 22 USdollars.
