The Giants signed a veteran free-agent catcher to a two-year deal with an option for a third. His name is Tom Murphy and he has just over a thousand plate appearances in the bigs (eight seasons) and over two thousand innings (261 games) behind the plate. Most recently he slashed .290/.335/.538 in 47 games (159 PA) with the Seattle Mariners. He's got some pop and is clearly going to back up youngster Patrick Bailey, the putative starter.
Blake Sabol, after surviving his rookie season and Rule 5 status, seems like the obvious backup to that tandem.