I am interested in working with BLE proximity sensor on iOS and have been looking up for a few answers to my query but could not find any solid ones.
1) Is there a
Theoretically, there is no limit to the number of Bluetooth LE devices that can be connected to a single iOS device (if the iOS device is acting as central and the LE devices as peripherals).
In practice, however, the limit seems to be somewhere above 20 LE devices being connected simultaneously to the iOS master. That number comes from both Bluetooth LE transmitter manufacturers and accessory developers that I've talked to. The exact figure will probably vary based on the particular iOS device involved and the transmitting properties of the Bluetooth LE accessories.