[Asterisk-Users] Group= equivalent for sip channels?

[Damon Estep]

With zap channels a group can be specified so the first available
channel is used, for example, the b channels of a PRI can be assigned
group=1, and the dialplan can specify dial zap/g1 to indicate a free
channel in group 1.

How do you achieve the same thing when the channels are SIP?

More specifically, lets say * is registered with 4 different SIP
providers and you want to make an outbound call using any one of the
providers that is not already in use. Would you have to set the dialplan
to go through each one until it can find a peer that accepts the call
request, or is there a smarter way similar to dial/g# with zap channels?