Mobile Challenge

Hi, we are a data security company and we have an interesting challenge in the mobile app world: We would like to send a security code that will appear simultaneously on the incoming call screen of the receiver's phone before he answers the call.
On top of that, we would like to send an additional security code during the conversation, and we would like it to appear on the receiver's phone screen (next/under the call ID and call duration) in real time. Any ideas?
Many thanks!

John