Passkeys are connection specific, meaning a new one is generated each time you go to pair a device. Both devices must enter the same passkey to pair with each other, but it is definable by you. So if I got to pair my N810 to my Bluetooth enabled phone and I started on the N810 side by going to Bluetooth Devices>New then select my phone, the N810 automatically generates a random code that I enter in to my phone so they can be paired. However I could change that code to 1234 and as long as I enter the same code on the other device they will pair. Keep in mind a new code is required each time you pair a device.

Put more clearly - there is no Bluetooth passkey on your N810 or any other Bluetooth device, just a one time number that has to match on both devices in order for them to pair.

Also remember that devices without any mode of input generally have default pair passkeys like 0000 or 1234. (think Bluetooth headsets), and of course the device you are trying to pair to needs to be in pair mode otherwise you won't be able to connected to it. Once the device is on the N810s trusted device list (ie: its been paired) it can open and close connections at any given time without having to put in a passkey or putting anything into pair mode.

I actually really like this protocol that is standard to Bluetooth devices. So someone can't hack your device and steal your passkey because you make a new one each time that has to match on both devices. I hope I explained that clearly, let me know if I need to reword it.