It is hard enough to drive a normal app var it’s UI, however when the app is not running on your development platform it is even harder.
So what tools will help me test
Expensify is definitely an option. Other than that there is Experitest. But Expensify does not support Windows Phone 8 and is terribly flakey after making changes to support windows phone 8.
I've not seen anyone release any tooling for this yet.
If you're going to try and write something yourself, you should have a look at this post on emulator automation and testing.
X-Ref with question 3806477
Expensify's (confusingly named) Windows Phone Test Framework supports UI automation. I've yet to use it on a project, but it looks promising.