OK,

Weird scenario, my players wanted to find the route a group was using to see if it was a predictable route. The Mage/PI wanted to use Detect Individual, ritually cast, to track their route. The target of the spell was willing, desired extraction, so they would not be resisting the spell. To the best of my knowledge this wouldn’t really have worked RAW, but it was a cool idea, that I knew would have little, if any, bearing on things in the long run, the targets used a randomly varied route.

This put me on an idea, how would you go about designing a tracking spell, one that would allow you to know in general where a specific target was and where they were going, within an area say the size of Seattle? Would such a spell be possible within the accepted limitations of SR4 magic? What would the parameters of the spell be?

why not use a spirit's search power?
mage:Search him and tell me where he is!
spirit:xy
mage:now do it again
spirit:xy
mage:and now again plz
...
as long as you have services ...

or invoke a great form and let him endow you Search

"Hey, I found your target, he's crossing N 130th street at 1st Ave NE. That's my service, see ya!"

Then you send a watcher

You mean a watcher spirit which--by RAW--has 2 dice to Search? Maybe four?

If the spirit already found the target, then assign a watcher to follow the target. Or even better, send a watcher with the spirit to begin with. Or tell your spirit to Find and then follow so it does it all as one service.

You could just give your buddy something astrally linked to yourself, and use astral tracking.