Hi,
Take a look at the UpdateCallVariableSampleGadget to see how to get the call variables from the dialog. Assuming that the outbound account number is stored in the BAAccountNumber outbound variable, you can get that information in the same fashion. You can use the browser's debugger with a breakpoint to see all of the variables in the list.
As far as displaying it on the screen, you can do something similar to how the external rest api same gadget displays the response, by just spitting it out to the screen as html. Another option is to the log it using the client logger, which you can see in the browser's debugger or in the client logs (after you submit them).
Thanx,
Denise