Normally the nRF5 has the peripheral role when connecting to smart phones. In this role only one smart phone can be connected at the time.
If the nRF5 has the central role it can connect to multiple devices that support peripheral role, so if the smart phones supports this. It is possible.
Edit 01.10.2015:
How would this work in practise? I
believe the device with the Central
role has to initiate connections, so
if a piece of equipment has a nRF51 in
a Central role and I'm nearby with my
phone then how do I connect? Do I need
to advertise and then wait for a
connection request from the nRF51?
Yes, the device in the central role initiate the connection by send a connection request. The phone would need to advertise, and the nRF5 has to scan. When the nRF5 scans an attractive advertising packet it can send a connect request to it. You would need to use the S120 or the S130 stack on the nRF5.
Also once the central nRF51 has
established a connection with one
phone, is it still able to keep
scanning (without breaking that
connection) in case a second phone
comes along and requires a connection?
The S120 is able to maintain 8 connections, while the S130 is able to maintain 3 connections as a central in addition to on connection as a peripheral. Yes, you can continue scanning after establising a connection, without breaking it.
How would this work in practise? I believe the device with the Central role has to initiate connections, so if a piece of equipment has a nRF51 in a Central role and I'm nearby with my phone then how do I connect? Do I need to advertise and then wait for a connection request from the nRF51?
Also once the central nRF51 has established a connection with one phone, is it still able to keep scanning (without breaking that connection) in case a second phone comes along and requires a connection?
