Mobile Visible Content

Hello

I have an app and I want to put an image on my site that when clicked will open up an opt-in box if the visitor is on a non mobile device or link to my app in itunes if they are on a mobile device.

I know that I can have content that is only visible on mobile devices, but can the mobile only content replace the non mobile content?

Effectively, I would prefer not to have two images visible at the same time. I would like the mobile link image to replace the non mobile link image if the visitor is on a mobile device.

I currently have the Aegaeus theme, but I will shortly be purchasing the Highend theme. So I would be interested to know if this work on both or neither.

Many thanks
Oretta