Per Pat Leonard, backup goalie Martin Biron is not in camp at the moment due to personal reasons. It is unknown how long he will be out. (Update: AV has stated there is no timetable for Biron to return, per the Rangers Twitter account.)
Leonard also noted that Johan Hedberg, most recently with the Devils, is in camp on a professional tryout. Hedberg’s tryout is interesting, since the Rangers are pretty set at goaltender this year. There is likely something that we are missing. Who knows, maybe they just want to talk to him about how backup goalies tend to look like Patrick Roy against the Rangers.