The PCs exploring Felltower fairly routinely include wizards with the spell Wizard Eye. I noted in a previous game summary that I don't count exploration via Wizard Eye to be worth XP.
This is why.
Wizard Eye doesn't involve any risk. Risk of detection of a nearby wizard, yes. But of where that wizard is, no. Of setting off traps meant to kill, main, or annoy delvers, no. Of falling into dangers of any kind, no. It doesn't even cost a lot to cast - and it's trivial for wizards to get it high enough to be free to maintain once cast for a pittance of FP.
XP awards are meant to drive two kinds of behavior - taking risks for profit, and taking risks to discover things. It doesn't hurt that discovering things you can exploit for wealth helps profit, and profit helps improve your ability to explore and exploit wealth.
Giving XP for areas explored by Wizard Eye would be akin to giving XP for money earned in town or generated through non-exploration activities (mining or trapping in a safe area, for example, or payment for a job.) It would also result in XP being given to characters who are guarding the wizard but aren't actually even seeing the areas they are getting XP for "exploring."
I don't allow Invisible Wizard Eye and I don't allow people to cast Invisibility on a Wizard Eye to get around that. (Or put any other spells on it, either.) That plus Dark Vision and See Secrets on the caster would be a nightmare from a play perspective - just casual exploring, mapping, and zooming around cataloging monsters and treasures for extended periods while the other players sat around trying to keep themselves entertained. If that also gave XP, it would be pretty trivial for the players to "earn" 2 xp for exploration every session without real risk.
It's a nice spell for the PCs, and I don't mind it - but I do mind letting it be spammed out and abused to explore large areas of the dungeon so the PCs can earn XP for not taking risks.