Hi,
Is there any way we can connect to other BLE devices apart from iPhone's BLE, since I am not able to connect my BLE hardware device from Watch OS?
Bluetooth Connectivity on Watch OS
Yes you can connect to CBPeripherals on watchOS. Check out thew WWDC video for details, I forget which year it was, but one outlined some limitations on both watch and tv if I remember correctly.
Something like up-to two peripherals per system, not per app as you may expect. This would not count the iPhone, or so I would expect. Additionally the connection interval is limited to 30ms.