Don't think I quite understand what you are trying to do.
but every service on the client side can show the throw message by showing [server-message]
these will show up as an Alert drop down
Other ways to get custom messages to the client side would be to load them up in a Stream/Blog and display them in a mashup
Am I correct in thinking that you have a remote Thing that is attempting to trigger a service of a modelled Thing on the Platform?
If so, when you trigger that service it is being run inside the platform JVM, so you're not going to get exceptions coming back as part of the stack trace. You can get around this by setting up your platform service so that it returns an infotable containing any returned values from the service plus status information. Your code on the device then needs to parse the InfoTable to get either the success or failure messages and process accordingly.