Apple turns out to be very restrictive about Bluetooth communications for iOS platform.
Focusing about a native application with Xcode (but not PhoneGap based - PhoneGap is a Xcode plugin that allows web apps to be converted into native ones; btw it gives a quite nice but limited access to underlying hardware resources) for a iOS device to communicate with bluetooth devices (even with discovery actions) the following conditions have to be met:
-) The device you're trying to discover must be equipped with Apple Bluetooth authentication chip (you can ask to Apple directly for the MFi program);
-) Internally your app must declare a protocol name (e.g.: net.yourcompany.proto0) which the devices you connect with must conform to;
-) You must use Apple's External Accessory Framework to establish communication with such devices.
In short, by this procedure Apple guarantees that the only Bluetooth communications an iOS device can establish are just with authorized and certified Bluetooth devices.
I've gone 400 Mph about this thing but I hope it can give you some pointer to start your search.
The topic is too wide to be treated here in its full length.