>>What would be the easiest tool to write an app for Android?
You could consider Xamarin if you've already decided that C# and Visual Studio are your future, and are happy to hardcode your UI in Visual Studio or learn the new Xamarin UI- in which case you might as well consider dedicated Android options. For crossplatform there are other options like Rundev or even Lianja into which you can import existing VFP code before forging ahead with Python, PHP, Javascript or lots of other options that are not at the mercy of any single vendor.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1