So I emailed ZipWhip to find out if they would be making an app for Windows Phone 8, and here is their response:
Hi Dave,

As soon as Microsoft opens up their API’s enough to let us build an app we’re all over it. We would love to support the Windows phone.

Thanks,
Kelsey

I have heard this response from developers when asked about making a sound/vibrate/quiet toggle button. My question is, what API's are still not open? I am not a developer, and am coming from Android where everything was (mostly) open from the get go, so I am just curious as to what they are waiting on. Thanks!

BTW: If you do not know what ZipWhip is, it is an app that allows you to use any computer or tablet to send text messages from those devices, using your cell's phone number.

Thanks!