For the moment the web-based version of echoecho that Kate Russell referred to on BBC Click is a simplified version of the program that allows you just to REPLY to a "Where are you?" query that you receive from somebody else.
In an upcoming new version of echoecho - we will be extending the webapp functionality to include additional features of the main app.
In order to experience the webapp - somebody else needs to send you an echo - in other words - a "Where are you?"
If they do this (and you are not a registered echoecho user) you will receive an SMS from them containing a web-link. Opening this link will launch the webapp..