How to establish Bluetooth connection with a Bluetooth blood pressure monitor

You will almost certainly need an App from whomever made the BP monitor. Data from that device won't be over any standard BT protocol, so an app specifically for that device will be necessary to receive and interprete data from it.

So, for example, I know Qardio Inc. makes a bp monitor and they have their app in the App Store to pair with it. iHealth is another company that makes an automated BP device and has a companion app to log the data from it.

Follow the instructions in the manual for the device you're trying to connect to. Some devices require that you pair the device. Some devices rely on a special app installed on the phone.