Tell the UI why the device became unusable.

lib/roles/device/plugins/group.js

@@ -72,7 +72,7 @@ module.exports = syrup.serial()
       }
     }
 
-    plugin.leave = function() {
+    plugin.leave = function(reason) {
       return plugin.get()
         .then(function(group) {
           log.important('No longer owned by "%s"', group.email)
@@ -86,6 +86,7 @@ module.exports = syrup.serial()
           , wireutil.envelope(new wire.LeaveGroupMessage(
               options.serial
             , group
+            , reason
             ))
           ])
 
@@ -136,7 +137,7 @@ module.exports = syrup.serial()
         var reply = wireutil.reply(options.serial)
         grouputil.match(ident, message.requirements)
           .then(function() {
-            return plugin.leave()
+            return plugin.leave('ungroup_request')
           })
           .then(function() {
             push.send([
@@ -154,12 +155,12 @@ module.exports = syrup.serial()
 
     channels.on('timeout', function(channel) {
       if (currentGroup && channel === currentGroup.group) {
-        plugin.leave()
+        plugin.leave('automatic_timeout')
       }
     })
 
     lifecycle.observe(function() {
-      return plugin.leave()
+      return plugin.leave('lifecycle_ended')
         .catch(grouputil.NoGroupError, function() {
           return true
         })