Well there are a number of things for you to consider here, let me shoot them at you (I hope you are wearing armor).
1: Flash requires software to run.. DOH. that's the little plugin that you get and it's stuffed where IE or NetScrap can find it (or Opera as in my case).
2: It may need to run under a web browser though I doubt it. It runs as an OLE object from what I can tell. I suggest your application create a window that an OLE object can used and let the flash DLL do it's thing.
3: Flash isn't a GUI, it's a packaged format for storing data that's run by a fancy DLL. That's about the some of it.
4: You will need to know the plugin details for the version of the flash player you use OR if you can find a stand alone version of the flash server and use that.
5: Licensing, you may need to find out the details of licensing to use flash for your application.
6: Interface, assuming you are using something PC centric for your 'ATM' you need a 'mouse' or 'keyboard' for flash to work interactively. Customized keyboards aren't hard to obtain (no you don't need to buy a PC keyboard and rip it apart either). The mouse can be a driver for a touch screen, not a big deal there either.
Have fun and remember that using other peoples software may be fast, but it's also complicated
Cyb