The Gaming Den

Singular item, designed solely to allow my cohort to hide in a corner without getting noticed...

Ring of the Shadowblending
Benefit: While active, grants the wearer +20 to Hide and Move Silently, along with Hide in Plain Sight. Most importantly, moving out of the square deactivates the item, requiring another standard action to reactivate.
Activation/Duration: Standard action, Concentration duration to maintain
Price: 3500gp

How's the wording and design? Any room for abuse?

You do know that a +20 Stealth item'd cost 80,000 GP (if it's considered 2 skills)? Well, this one's pretty worse, but not enough to cost more than 20 times less (and that if you think the constant item'd be balanced, which I already wouldn't feel so sure on). Also, it needs a CL, which I guess'd be ... pretty high.

The kicker is that the creature is not allowed to move, lest the HiPS/MS be deactived, no?

Or break Concentration for that matter. So I think it's priced okay.

I was going for a bonus to hide and move silently, rather than something like invisibility & personal range silence; thus allowing a chance of being noticed, as opposed to the binary condition of whether or not they have see invisible. That, and disguise self gives a similar modification (disguise instead of stealth), but I'm very much limiting mobility.

Why not just make it:

Ring of Shadowblending:
As a Full Round Action, you gain a +20 to Move Silently and Hide checks, in addition to having the Hide In Plain Sight ability. You may attempt a Hide and Move Silently check during this round.

Thought you couldn't give feats through items...

How did HIPS price out?

Uh.... you did give a bonus that's pretty close to Invisibility.

Not as much as Invisibility; but if they're taking 10, and can achieve +10 more via ranks and stat modifiers they "count" as being invisible (+40 to hide checks).

Also, See Invisible isn't the only way to blow through invisibility. In 3.5 there is no more of a binary approach to invisibility, the spell simply gives and epic boost to your hiding ability (+40 if you stand still, +20 if you move; low-ish level (lvl 5+) rangers, monks, ninjas and the like in regular 3.5 can detect a moving invisible target if they get a middling roll).

It's a non-combat item, and it's not a snipers item. Unless the sniper's a bard and has that one spell where they can maintain concentration on a spell for free. At that point, this is a pretty big combo.

From what I recall, +20 is standard for Invis, as long as you're actually moving around (doubled if you're trying to hide); and I thought that bonus was a bit too much. Also, it (invisibility) remains binary in that you retain total concealment even if someone makes the Spot check.

I thought about a ring of invisibility, realized it's price is about 40% of the formula, then 'invented' a 1st level spell with concentration duration and gave invisibility. Then I compared the formula of the ring to that, reduced in price by 50% for the 'no movement' option.

However, I didn't like the absolute nature of invisibility, so I changed it into +20 Hide with HiPS for a similar effect and added Move Silently for completeness.