This is my take on how stealth and perception should work. Having given up on being published under 3.5, I've decided to release it unto the world in hopes that D&D 3.5 (via Pathfinder) will live on a little longer. If Paizo publishing choses to use any of the following, all or in part, feel free, and if they'd like to credit me, they are free to credit me as "Mercestes D'Moriarty."
As always, I appreciate any feedback and/or comments.
Stealth
Hide and Move Silently are combined into the skill “Stealth.” Stealth is an activated skill and is opposed by a Perception check. Stealth encompasses all the skills of both Move Silently and Hide, as well as the knowledge to use terrain, camouflage, environment, circumstances, lighting conditions and your knowledge of other creature’s perception, vision ranges, and capabilities. This means that your ranks in stealth grant you insight into how to evade various types of perception, with the exception of Blindsense, Blindsight, and Tremorsense. Conditions such as lighting, cover, concealment, darkvision, lowlight vision, etc. can be reasons why a creature would be allowed a perception check, but never negates the need for a perception check. You cannot use stealth while being observed unless you have some form of concealment or cover, or you make a successful bluff check as a distraction (see bluff.) If you have concealment or cover, or you are not being actively observed you state that you wish to use your stealth skill and you make a stealth check. The stealth check becomes the perception DC to beat your stealth. That check remains to be the perception DC until you chose to no longer be stealthy, or you are spotted and observed by a creature. A successful Perception check means you have been spotted and are being observed, and you cannot make another stealth attempt until you become concealed, find cover, or are no longer being observed.
Extraordinary abilities which allow you to become aware of creatures which use senses other than sight or sound (Tremorsense, blindsense, blindsight, voidsense) are too exotic and/or powerful to be defeated by stealth, except under special circumstances. For example, you cannot use stealth against a creature with tremorsense unless you are flying or otherwise not touching the ground.
Special: Any race or class which provides a bonus to either hide or move silently instead grants a bonus to “stealth.” These bonuses stack from differing sources. If a source provides a bonus to both hide and move silently, apply the highest bonus only once. For example, the vampire template lists a +8 bonus for both hide and move silently checks. This translates into a +8 bonus to stealth checks.
Perception
Both Spot and Listen are combined into the skill “Perception.” Perception is an automatic skill that is “always on” and opposes a Stealth check. Your skills in perception include your ability to use your senses, identify and search cover, peer through concealment, and take advantage of whatever heightened senses you may have. You make a perception check, with the DC being the stealth check made by the stealthy character when he engaged stealth. Beating the DC means you have spotted the character and are now observing them. Failure means that the stealthy character has evaded your senses (even your heightened senses) and are unknown to you. Generally, perception checks are made by the DM without the player’s knowledge whenever they encounter a hidden creature or other feature that can be “spotted.” Enhancements to your vision or hearing can provide more opportunities to make a perception check (IE: darkvision allows you to make a perception check in complete darkness) but it never negates the need to make a perception check.
Extraordinary abilities which allow you to become aware of creatures which use senses other than sight or sound (Tremorsense, blindsense, blindsight, voidsense) are too exotic and/or powerful to be defeated by stealth, except under special circumstances, and negate the need of a successful perception check to become aware of them. However, a successful perception check would allow you to be aware of the creature using your mundane senses in addition to your extraordinary senses.
Search
Search, while similar to perception, is different in a few key ways. First and foremost, search is an activated ability, not an automatic ability. One can spot something due to their high perception, a player must state that their character is searching to use a search check. Search allows you to spot traps, notice hidden doors, sense pit falls, separate treasure from trash, find gold hidden on a person, or otherwise find things which are hidden, but not by the usage of a stealth check. Generally, only animate creatures can use stealth checks, which is opposed by perception, and unattended inanimate objects have a search DC. The search DC varies, based upon the difficulty of the trap, the difficulty associated with finding the item in question, the surroundings, etc, and are determined by the DM.
Special: Elves recieve the "Elven Perception" feat for free as a racial feat. With Elven Perception, search becomes rolled into the skill “Perception,” not only negating the need to put points separately into the search skill, but also making search an automatic ability as part of perception. Characters with the elven perception feat can now “perceive” hidden doors and traps, as determined by secret DM rolls. Half-Elves do not recieve the feat "Elven Perception" for free, but may chose to take it as a regular feat.
Alertness
The Alertness feat grants you a +2 bonus to all perception checks. This bonus even applies to search checks made as part of perception by characters with the “Elven Perception” feat.
Stealthy
The Stealthy feat grants you a +2 bonus to all stealth checks.
