Is your problem specific to connecting to the BP Meter using the IPhone (that is, can you successfully transmit data from it using another device - e.g. USB stick + PC)?
If you can't communticate with the device at all, the ANT+ Forums are probably the better place to ask for help. Each of the devices has its very own peculiarities, so including information on which device from which manufacturer you wish to connect to might be useful as well.