perhaps not where your question is intended, but if you're looking to have wristband access for your Gen2, you could also use an Apple Watch which can hold Apple Car Key to unlock/drive the car without your phone.
Maybe this will be helpful to explain how Car Key works. It's a video from Apple directly explaining how the technology works:
What's important to note is that Car Key relies on both ultra wide band (UWB) as well as Bluetooth Low Energy (BLE). While Gen1 Rivians have BLE, they don't have UWB...