While on the beach, Doyle is twice seen wearing a wedding ring. The first was brief, when Nadia confirmed that Phillip Bauer had hacked into their system and he reached up to adjust his comm unit in his left ear. But later, he again adjusted his comm unit while she was lecturing him on not being authorized to recover Josh before the component was back at CTU. That time, it was *very* clear he was wearing it. Throughout the season, his left hand is clearly visible without the ring. Presumably, this is Rick Schroder's own ring, and he forgot to take it off.
Prior to Morris placing a call to Security to have them escort Marilyn to Holding, he is wearing a Bluetooth headset on his right ear. When he makes that call, he lifts the receiver with his right hand and places it to his right ear (and the headset is missing). When he hangs up, he takes the receiver from his left ear with his left hand, and the headset is back on his right ear.
During the Oval Office phone call between VP Daniels and President Suvarov, Karen Hayes' cell phone rings. She reaches into her pocket to retrieve it and excuses herself, stepping out of the Oval Office into the hall. But when we cut away to her in the hallway, it is not a cell phone she answers, but a cordless land line.
At 13:29 Mike Doyle turns and yells to the chopper pilot to leave the area. And the chopper leaves. All this while the chopper is on idle. The pilot would not have heard him over the engine and chopper noise. If he had a com unit direct to the pilot he wouldn't have had to turn to the pilot to yell instructions at him.