Add logcat.

lib/roles/device.js

@@ -30,6 +30,7 @@ module.exports = function(options) {
   var services = {
     input: null
   , monkey: null
+  , logcat: null
   }
 
   // Show serial number in logs
@@ -229,6 +230,13 @@ module.exports = function(options) {
             })
         })
     })
+    .then(function() {
+      log.info('Launching logcat service')
+      return adb.openLogcatAsync(options.serial)
+        .then(function(logcat) {
+          services.logcat = vitals.register('device:logcat', logcat)
+        })
+    })
     .then(function() {
       log.info('Ready for instructions')
       poke()