One member of the party that I am GMing may put on a Dungeon Ring (prisoner) soon. The jailer does not know them, but might use "Scry" or "Teleport"to find out his lost ring's whereabouts. I don't understand the will save rule here. How high is the DC to resist the scrying or teleporting? (Somehow I may be too stupid to find out the variables that lead to the correct DC.) The jailer is just a medium level rogue, so has no classes in wizard or the like.
Without the abilities to cast the spells in question(be it as a spell, spell-like, by UMB or other) a Dungeon Ring(Prisoner) doesn't do anything other than provide the holder of the Dungeon Ring(Jailor) the ability to know the Status of the prisoner.
For the purpose of the spell Scrying: If the subject is Familiar to the the caster of the spell, then they receive a -5 penalty to their will save. If the Rogue is using a scroll, the minimum DC for the spell is 16(with a -5 penalty for the target).
For the purpose of the spell Teleport: If the subject is Familiar to the caster, then when they roll on the percentile accuracy chart, a roll of 1-97 is arrive arrive on target, 98-99 is off-target which is a random direction in a random percentile distance(of the distance traveled), and 100 is arrive in a similar area to where you wish to arrive, and if there is none in range the spell fails.