According to this document and this whitepaper, there are security measures designed to prevent passive eavesdropping a Bluetooth BLE connection. Is there a way to implement the secure connection between an iOS central manager and a peripheral device?
Specifically, I'm looking to implement "Just works association model". I want to know if it is possible with an iPhone.
EDITED:
According to the table under Step 4 in this link, because your Central (smartphone) has both Keyboard and Display, the only way to perform Just Works pairing is if the sensor has no input and no output capabilities.
So, to do that, you must configure the sensor to send a Pairing Response with the IO Capabilities set to NoInputNoOutput.
That will force the Central (your iOS device) to perform Just Works pairing.