Actually no, the keycard is a fully functional device just like a phone.
What is for limiting is Valet Mode. Set the passcode either in the car or app and valet mode is enabled until the passcode is entered again.
When Model 3 is in Valet mode, the following restrictions apply:
• Speed is limited to 70 mph (113 km/h).
• Maximum acceleration and power are limited.
• Front trunk and glovebox are locked.
• Home and Work locations are not available in the navigation system.
• Voice commands are disabled.
• Traffic-Aware Cruise Control is disabled
• The Mobile Access setting is disabled.
• HomeLink (if applicable in your market region) is not accessible.
• Driver Profiles are not accessible.
• The touchscreen does not display the list of keys that can access Model 3 (see Managing Keys on page 7).
• Wi-Fi and Bluetooth are disabled. When Model 3 is in Valet mode, you cannot pair new Bluetooth devices or view or delete existing paired devices.
yep - sounds just like Valet mode.
Easier to ask what problem you're trying to solve
Putting the app on somebody else phone means their phone always has a connection to your car - not a good idea.
Its designed for family, co-owners etc. Not designed for someone you want to let have a quick drive.