Gnome 3 developers have dropped this from gnome-control-center with a recommendation that it be repackaged and available as a separate application.
A launchpad wishlist item was requested.
An alternative in for typing break is workrave. It is now available as a backport:
sudo apt-get install workrave
You need to white-list this application to appear in the Unity indicator-applet. Read this question if you want a more detailed explanation about what to do.
12.04 and 12.10
An enterprising developer has resurrected DrWright for Precise. The package is available from a PPA:
sudo add-apt-repository ppa:drwright/stable
sudo apt-get update
sudo apt-get install drwright
Note, that for 12.10 the quantal ppa is not up to date, so you have to use precise repositories:
deb http://ppa.launchpad.net/drwright/stable/ubuntu precise main
deb-src http://ppa.launchpad.net/drwright/stable/ubuntu precise main
Find the applet in the Control-Center to launch:
image and source for the information
In a similar manner as for 11.10, workrave is available from the Precise Universe repository if you do not wish to use a PPA.