The invisible eye revealed, enchantment

So our covenent is concerned about magical scrying on some secure areas of our castle. I am looking to design a enchanted item which will alert us to any such scrying. The spell "Invisible eye revealed" seems to do what we want, but how woud you invest this in an item?

Can an item invested with an intellego spell alert those in the area that it has detected something, or does that require a linked effect? Creo Imaginem for instance to start shouthig ALERT! ALERT!

So I put this out as a chalenge: can anyone here invent a spell capible of detecting all non-ritual scrying atempts in a single area, with a maximum effect level of 35? The item should activate automaticly at sunrise and sunst to maintain continuous coverage. If not, how close can you get?

If the item was a bell or something similar I would consider the alarm a cosmetic effect (similar to the mist in frosty breath of the spoken lie).

But with duration: sun (+2magnitudes) and target room or structure (+2 or +3magnitudes) 2 uses pr day(+1) and an environmental trigger(+3)
the spell can only detect intellego spells up to lvl 22 (room) or 12 (structure)

Does it need room? Put the item in the room. Give it "personal" If someone looks into the room it will see the object and trigger the spell.