Magical Bug

[Cicciograna]

Hi there. One of my players wants to create a magical device acting like a bug, to drop in the lab of a wizard and eavesdropping him. He's a bit low on cash, so I put some limitations on the object, and made up this.

Magical Bug

This small object (a crystal, a scarab, a brooch, or even a stone) works as an eavesdropping device, specifically attuned to a particular target. It must be attuned to the target: the person who wants to eavesdrop (let's call him th "wielder") has to pronounce a command word and then it has to make the Bug "hear" the target voice. The wielder knows if the Bug has succesfully attuned to the designated target. Once attuned, the Bug can be left anywhere, set in a chandelier, hanged to a wall, used to craft the floor of a room, etc., but when it hears the voice of the target it activates: it transmits the target voice (and any sound in the surroundings) to the wielder as per the spell Clairaudience, and up to 10 mins per charge. It has 10 charges, that refill every day.

No Aura; CL 10th; Craft Wondrous Items; Clairaudience/Clairvoyance, Price: 17000 mo.

I put many limitations on this object. It doesn't work continuously, and every time it works, it's just for 10 minutes; it is attuned to a single person, so if this object is left in one room, and the target is not present, it's useless; it has to be attuned, and this could not be simple.
I think the pricing is correct, given that I checked this page first:
Random Encounters: Nasty Surprises - Part 4
and the Eavesdropping weapon enhancement is way far better.
Give me your advice on what do you think of this item and how to improve it, if needed.

[SSuser]

If he is low on money then I'd suggest scrying on the guy.

[Cicciograna]

Apart from the fact that Scrying gives just a visual image, while he needs to hear the wizard, there are some campaign factors for which ha cannot use the spell and instead needs the magic device (he doesn't have access to the spell, and needs to have the informations often; the magic device is a fire-and-forget solution, while the spell has to be cast many times, and the casting time isn't the shortest).
Anyway, my question was about the pricing of the item: I don't want this sort of item to be too cheap (or too expensive), lest have an abuse of it...

[SSuser]

Scrying, fifth word in the spell description.

Alright then if scrying won't work, I think the item functions too many times per day and is too expensive. I'd cheapen the cost, have it function about 3 times per day, and be detectable.

[Cicciograna]

Sorry, we just began playing 3.5ed, and I still have to learn all the spells...

Anyway, the item is so expensive because of the high number of uses per day: maybe 10 charges is indeed to high, but this item is intended to detect wizard's voice when he makes plans with his minions and gives them instructions, and this would occur about 2 or 3 times per day and for about 20 minutes each time, so this explains the "10 times per day, 10 minutes each time"; for what concerns detectability, it was a hard decision whether or not to incorporate it, but I thought it would be pointless to have a detectable bug; anyway, I think I'll cut it to have a break in price; by the way, 17000 gp is affordable by the PC.