This is a complete tutorial, discussing how to build a simple calculator app for Android. Check it out, and implement some of the recommended improvements.

Talking to VISA is a well-trodden path, for example if you are a Python coder there is a wrapper called PyVISA through which you can command your instruments to your heart’s content.

Just make sure to ask ChatGPT to spit out the code in the Python language (so literally you should ask “Create a working calculator in Python code”).