Over in the Spell Auto Re triggering thread @loke shared his Rusticani enchanting a rope to create a Circle Demon's Eternal Oblivion. I was pondering how to make that even sneaker... and mused a bit further afield.
You can make a permanent illusion with a Creo Imaginem Momentary ritual. Let's say you make a big permanent circle of the smell of roses.
Then, enchant it. There's no "illusion" material listed on the Material And Size Table, but fortunately we can make it a compound item and place a semi-precious gem or something that's part of the circle of rose-smell.
Everything that crosses the circle of rose-smell should get Eternal Obliviated. If the circle gets disrupted, the enchantment should re-trigger the effect. It may not even be necessary to make an enchantment if you use the permanent illusion circle of rose-smell mark your casting Circular Demon's Eternal Oblivion. There's not a physical manifestation of the illusory odor, so I'm not sure what could disrupt it aside from Imaginem magic -- wind, etc shouldn't affect it.
However, I do like the idea of enchanting an illusion. Seems like there should be lots of useful applications for this...