How to get list of available Bluetooth devices?

This guide looks promising for Bluetooth 3.0. Remember that the CoreBluetooth framework is ONLY for Bluetooth Low Energy (4.0). At bluetooth.com's dev-pages you can see some examples of globally defined services, and as Guan Yang mentionen, you can see that the heart rate service is 0x180D. UUID`s of the unit is defined by the manufacturer.

Here's a code snippet to maybe help you along the way.

// Initialize a private variable with the heart rate service UUID    
CBUUID *heartRate = [CBUUID UUIDWithString:@"180D"];

// Create a dictionary for passing down to the scan with service method
NSDictionary *scanOptions = [NSDictionary dictionaryWithObject:[NSNumber numberWithBool:NO] forKey:CBCentralManagerScanOptionAllowDuplicatesKey];

// Tell the central manager (cm) to scan for the heart rate service
[cm scanForPeripheralsWithServices:[NSArray arrayWithObject:heartRate] options:scanOptions]

in Bluetooth, there are "Services". A device publishes 1..N services, and each service has 1..M characteristics. Each service has an unique identifier, called UUID.

For example, a heart rate Bluetooth Sensor that offers the service "heart rate", publishes a service with UUID 0x180D.

(more services here)

So when you perform a search, you must provide a UUID as the criteria, telling which service to search.

You should take a look at one of the examples. Here’s the relevant line:

[manager scanForPeripheralsWithServices:[NSArray arrayWithObject:[CBUUID UUIDWithString:@"180D"]] options:nil];

(I know this is a Mac OS X example, but the iOS CoreBluetooth API is very similar.)

CBUUID identifies services you are interested in, not devices. Standard services have a 16-bit UUID, in this case 0x180d for the heart rate monitor or perhaps 0x180a for device information, while proprietary services have a 128-bit UUID (16 bytes).

Most devices implement the device information service, so if you are just looking for any device, you could try [CBUUID UUIDWithString:@"180A"].

Try giving this while you are scanning for devices

NSDictionary *options = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:NO], CBCentralManagerScanOptionAllowDuplicatesKey, nil];

 [self.centralManager scanForPeripheralsWithServices:nil options:options];

you will be able to get the list of devices at didDiscoverPeripheral delegate method