Update useful-mobile-apps.md (openaps#1157)

Addition of SerialBot app for Android devices to login to rigs via mobile phones, useful for offline looping.

Author: GlennCoco

docs/docs/Customize-Iterate/useful-mobile-apps.md

@@ -127,6 +127,12 @@ Perhaps a more slightly advanced-user (or curious-user) feature of SimpleSSH is
 
 ![SimpleSSH navigation example](../Images/navigate.png)
 
+## SerialBot (Android)
+
+This app is useful for logging into the rig via a terminal session when not near a computer or using offline looping, can be done via USB serial cable, bluetooth or wifi depending on your setup. Simply selecrt the connection method using the drop down box and type in the rigs connection details.
+For SSH use the format root@yourigname/ipaddress:22
+This app will use the same commands as other terminal session apps such as PuTTy.
+
 ## Nightscout Apps
 
 There are a few useful apps for viewing and maintaining your Nightscout site.