What? I can't hear you!!

[SangoProduction]

1,090 feet of conversational distance (in either direction), because take 10 and +99 bonus to perception check, and each 10 feet adds +1 DC to the base 0 of hearing the details of a conversation.
How:

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Let's see: Inquisitor8/Wizard1/Sleepless detective1 so also lvl10 and all 1st party sources.

Eyes of the Eagle +5 Competence bonus (2.5K)

Xorn Robe +5 Untyped Bonus (20K)

Demon Senses +8 Racial Bonus (20K)

Acute Senses +30 Enhancement Bonus (800GP scroll Inquisitor2 1Min/lvl CL 16)

Hunter's Blessing +4 Sacred Bonus (1625GP scroll Inquisitor5 1hr/lvl duration CL13)

Pattern Recognition +10 Insight Bonus (500GP 10min/lvl scroll Wiz/Sorc1 CL20)

10 Ranks

3 Class Skill Bonus

+6 Wisdom mod (18 start same as your character's primary attribute +2 level up +2 Enhancement item 4K GP)

+4 Alertness

+6 Skill Focus

+2 Int Mod (14 Int same as your character starting)

+1 Trait (Seeker)

+3 Familiar Bonus (Hawk or Owl)

+2 Aid Another from Familiar

99 so far. Maximum 119 check.

So, aside from the all seeing eye of the city just casually hearing every single conversation in the town, what are the most interesting ways of using this perception bonus?

[Manyasone]

Good luck filtering out... everything...

[SangoProduction]

Good luck filtering out... everything...

Oh right. Terrible conditions reduce the potential range by 50 ft. I think I can live with it.

[The Glyphstone]

You'll be like Lex Luthor in that S:tAS episode where he gains all of Superman's powers, including his microscopic vision, and is effectively paralyzed by the overwhelming epiphany that results.

[AnimeTheCat]

Also, is the distance determined based off of a straight line, disregarding line of sight and line of effect? I would think that obstructions would either change the distance or increase the DC. Either way, you're really high level, being really good at seemingly simple things is kind of a given.

[Segev]

In your lair/dungeon/whatever, you have endless self-resetting "traps" that are basically very quiet noisemakers with unique sounds. They're near various remote-triggered traps you control; you wait for people you know the number of by listening to them talk and their conversations to walk by, timing the trap intelligently and possibly taunting them via some sort of distant-speaking magic or mechanism.

Use this all-seeing-eye stuff to know where people looking for you are, and to avoid them by never letting them get close enough to hem you in.

With distant-speech magics of any sort, you can serve as a relay for conversation/mission control. If the whole party has this super-high perception, you can carry on conversations from across the dungeon (provided the dungeon is small enough that the added walls don't reduce distance of your Perception below the distance you're separated).

Have extremely quiet conversations that nobody without your super-hearing can hear.

Practically never fail to pinpoint creatures you can't see.

Use only clairvoyance to both see and hear at your target location.

[SangoProduction]

In your lair/dungeon/whatever, you have endless self-resetting "traps" that are basically very quiet noisemakers with unique sounds. They're near various remote-triggered traps you control; you wait for people you know the number of by listening to them talk and their conversations to walk by, timing the trap intelligently and possibly taunting them via some sort of distant-speaking magic or mechanism.

Use this all-seeing-eye stuff to know where people looking for you are, and to avoid them by never letting them get close enough to hem you in.

With distant-speech magics of any sort, you can serve as a relay for conversation/mission control. If the whole party has this super-high perception, you can carry on conversations from across the dungeon (provided the dungeon is small enough that the added walls don't reduce distance of your Perception below the distance you're separated).

Have extremely quiet conversations that nobody without your super-hearing can hear.

Practically never fail to pinpoint creatures you can't see.

Use only clairvoyance to both see and hear at your target location.

Nice. Thanks.