The Mobile Module on the current 7.5 LTS and 7.6 releases, in fact, requires Java 7.
jasoncoope, the updates are indicated by the 3rd digit in the version number, so 7.5.11 is the updated (5 updates up) version, and it works with Java 7. If you absolutely have to stay on 7.5.6, you can still use Java 7 for the Gateway (specifying the path to it in /Inductive Automation/Igntion/data/igntion.conf file), while pointing the Mobile Module to Java 6 by specifying the full path to it in the “Java Path” setting on the “Configure > Mobile / Settings” page.