Power Synergy

[Becq]

If I recall correctly, it was stated in the series that evocation could not be directed by way of magical abilities such as thaumaturgical clairvoyance.  Magically-enhanced vision toes that line, but my own opinion would be that if a mortal eye can't pick up the photons bouncing off the target, then its not really 'line of sight'.  But that's my opinion; RAW is a bit vague on the subject (though it might be worth noting that the RAW states about Evocation that "you cannot attack a target that you see through scrying or some other effect."

[ways and means]

I always assumed that just meant you couldn't do it through a relay like through a crystal ball or through a TV camera to stop long range indirect evocation.

[devonapple]

In point-based games, "Indirect" is a power modifier used to modify a ranged attack, and depending on how much you pay into it, the origin point of your attack can be anywhere (even behind a barrier), and you may even be able to rotate the vector of the attack to something other than straight from you (possibly blowing someone back towards you). In the books, Dresden often opens emergency doors from the outside by creating a burst of force from just the other side to trigger the emergency exit mechanism. This would be a canonical example of an indirect spell effect, one which even violates the traditional "line of sight" rule.

That said, one could adapt it to DFRPG in a variety of ways.

Possibly add X shifts to overcome whatever zone border is in the way.

Create and then Tag a relevant Aspect like "Summoned Demonlings" to narrate that your "attack" is actually being carried out by little independent demonlings who pop out of flaming circles in the ground next to your enemy, justifying the "indirect" attack. Dresden may be Declaring the Aspect "Emergency Exit" and then Tagging it to open the door.

[Becq]

I'm not sure where the dividing line was intended to be.  I would probably allow evocation through glasses (because banning wizards from using glasses just seems silly) and through optical binoculars (because they are just more elaborate glasses), but not through electronic enhancement technology like IR binoculars (which would blow up as you drew power any way) or magically-enhanced vision like clairvoyance or supernatural senses.

But I can definitely see powers that enhance what your natural eyes can pick up as being a pretty big grey area, so go with what feels right to you.

PS: There's also potential balance issues that might be worth considering.  A character that can cast spells through solid walls is likely to have significant advantages over other characters.