If you were to put a watching ward on someone is that considered a constant effect until it's triggered?
Could be.
Altho' the final effect hasn't been triggered, that person could be interpreted as being subject to the magic of the "watching" part. That is, the Rego Vim surrounding them is an active magical effect, and one as large as the final spell effect, regardless of the final effect or duration of the other.
Or not. Sounds like something to be HouseRuled.
But, for me, I'd go with "yes". Feels close to the same thing, walking around with magic surrounding you all the time, regardless if that magic has a currently tangible effect, or is simply potential - the magnitude of the effect is the same, in Hermetic terms, regardless of that effect to mundane senses.
Or, look at it another way- if an InVi spell were cast on the person in question, what would it find? Well, some big-ass long-term spell! And if so, is that a "magical effect"?... Yep, sure is, even if it's not "doing" anything that effects the mundane at that moment, like teleporting them, or giving them the strength of a bear, or sending a warning to the casting magi, or whatever.
I'd say it's the magic, not the effect, that causes the warping, just like an aura.
(And in terms of Game Balance, a wise SG discourages every grog, dog and barn cat walking around with huge watching wards on them.)
(And I would also rule that the triggered effect would potentially be a second, short-term different source for warping, if it were large enough. The spell description says "another spell", so the two aren't the same there.)
On an actual person? I'd say yeah. On an item someone carried around? Nah. Am I being a bit arbitrary? Absolutely.
That's not "arbitrary", that's by the RAW, which read (p 167 ) "...being subject to mystical effects..." While it may seem like a cheezy way around the penalty, it's perfectly acceptable by the rules.
Now, ~I~ might have that item suffer some warping over the years, and certainly make the character aware that there are downsides to having to carry an item, as well as having that item trigger the spell, but, as a concept, I'd say that if you're not the target of the spell, if the item you're carrying is the thing holding that enchantment, then you're not the subject of the mystical effects (for purposes of this discussion).
Note that if the item were monitoring the person as a triggering mechanism, perhaps their state of physical or mental health, or something similar, then that could be interpreted to "being subject to mystical effects". It is a Ritual, so it's not a cheap substitute for one-use items. ymmv.
It's not actually a watching ward, but a mystery combining the bargain and until durrations. I figured it'd work the same as far as warping goes. And while the magus allowed it to be cast on them, it was while facing the possibility that "if I don't agree my body may never be found, and I won't get what I came here for"