It really depends, I think. Mostly though, they will just be aspects, and can as such do what aspects do. Which includes canceling out other aspects (night vision vs. darkness, grappling hook + rope vs. smooth wall). So they basically make the action the player wants to do possible, and should not grant a +2. If the action would be possible, but the equipment makes it easier, I'd let them invoke for a +2.
If it makes sense to be in the characters permanent equipment, then I would probably let him use it on every similar problem in the future without spending a fate point. If not, he would have to find a new solution. Or I as a GM have to find a new problem to throw at him, if the player has all the solutions to my regular problems readily at hand.
Another way to go, and a good one at that, would be to treat items as characters. Those characters can have stunts and powers, and the player using the item can benefit from the item. That is especially useful for equipment heavy characters, because I think it is highly irritating and unfair, if they can buy something and use the tag for free, but every subsequent invoke will cost them a fate point, although they purchased the item and it is in their hands. Just doesn't make much sense to me, even though I otherwise like the fate point mechanics.
So it could be
Mike's trusty Grappling hook...
- aerodynamic hooks (+2 might for attempts to throw the grappling hook)
...With rope
- Evenly spaced knots (grants +1 on athletics when climbing a wall with uneven surface and allows to climb a smooth surface at all)
Expensive Night Vision Goggles
- Bright as Day (Wearing the NVG cancels out any "darkness" or similar aspects)
- Infrared (In the absence of other heat emitting sources, living targets light up bright as day. +2 alertness for spotting anyone while wearing the goggles.)
And so on, you get the picture. I'd be reluctant to let someone do this for conflict related items, but for something like this, that will probably come up once, maybe twice, it should be fine.
Or you might even give a character a "companion cube" item, that is an actual character on his side, like Tim the Sniper, the example character in the books. Make his sniper rifle a character, with its own aspects and skills, and even give it an action, that it can use to maneuver for Tim. In the narrative, that's all Tim acting, he knows his rifle so well, that he can "feel" how to best aim his shot, and that is reflected in the mechanics of the gun placing an aspect. You can always factor in the gun as a character, when calculating the opposing npcs power level, so it should even things out.