Ledger Nano X, a popular hardware security device (as well as one of Casa's supported hardware devices), has a Bluetooth functionality built in from the manufacturer, which allows it to connect to the Ledger Live app suite.
When you use a Ledger device with Casa, you are using the device in a different way. Rather than being it's own single-signature wallet, Ledger is simply one of multiple signing keys in a larger setup when it's added to Casa. Casa even uses a unique web interface to facilitate signing transactions from Casa App.
Because of Casa's current implementation of our secure web interface, you cannot currently use the Bluetooth function on the Ledger Nano X to connect to Casa when applying transaction signatures. You must physically connect your Ledger to your laptop or desktop computer via a USB cable that is capable of transferring data (not just charging). The cable that comes with your Ledger device should work fine for this.
If you use also your Ledger Nano X to secure assets outside of Casa, via Ledger Live app, then you should be able to use the Bluetooth functionality to facilitate those transactions through Ledger Live.
It's possible that Casa will offer the ability for Bluetooth-based signing using the Ledger Nano X in the future, if it can be done in a way that matches our security standards.
Don't have a Ledger Nano X yet? See our article Where to purchase a Ledger device for info on where to get one.