The most efficient and timely mechanism would be to write messaging into the programs. The programs would write to a log file on a server indicating received, started, step 1, step n..., completed or whatever information you need.
SMS doesn't have a way to indicate what order clients are lined up to receive advertisements since it's the client itself that determines when it is going to wake up and sniff for ads. I suppose you could check agent times to figure out what schedule a client is on then interpolate what the order might be.