SMBs that you can inflate underwater and send up (DSMBs really) are very useful for dives with strong current where you may not be drift diving. I was recently the boatman for a dive where so long as the divers stayed closed to the rocks they were sheltered from the current. If they moved to far out they would very quickly get blown away. If that did happen then if they sent up the SMB while on their safety stop I would have been able to ready the boat and be tracking with them before they drifted too far away. This would be rather than them being much further away and thus more difficult to spot when they did surface and inflate their Sausage.
When ever I have skippered the boat I have made sure everyone had a Sausage at least though. You can get a stack of very cheap ones and give them out, if someone doesn't return one it isn't the end of the world.
ADDENDUM:
The safety device I have heard a lot of praise for is a mirror. If you are in the states you can get one from DAN pretty cheaply, in Canada you pay through the nose for shipping and anywhere else they won't send it to you Failing to find one that would survive being immersed I settled on a CD I picked up when packing the car for a dive trip
When ever I have skippered the boat I have made sure everyone had a Sausage at least though. You can get a stack of very cheap ones and give them out, if someone doesn't return one it isn't the end of the world.
ADDENDUM:
The safety device I have heard a lot of praise for is a mirror. If you are in the states you can get one from DAN pretty cheaply, in Canada you pay through the nose for shipping and anywhere else they won't send it to you Failing to find one that would survive being immersed I settled on a CD I picked up when packing the car for a dive trip