Black Cat Systems has produced a simple iOS and Andriod App that will let you send Codan* (and other tones such as DTMF, CTCSS and many HF radio communications formats) from your smart phone over the radio to connect to and interact with many radio communications standards.
*23/8/13 the app has seen a version update, the timings can be adjusted now.
Many of the older generation Codan HF radios don’t come standard with selcall, and a number of my ham friends have old codans that do have selcall as their base rigs. The ability to call them from my home Icom is handy. This app allows you to send these tones on any radio!