As discussed in the SDK Dialog, you can send a presence update to a specific user, with relevant information as note. This text will be rendered on the App Icon on the homescreen.

An example to send presence updates can be found here:

https://github.com/innovaphone/jsbadgeexample

You have to use the "note" property of the "fty" object to set the required text.

Best Regards

Andreas Fink