Hans Rey introduced us to this chap, casually walking the aisles of the Sea Otter with his Laguna Rads T-shirt on and his wearable tools on hand…
Launched via Kickstarter, the Wheelie Wrench (there are other versions for skate and snowboards) is a slim multitool small enough to fit in the coin pocket of a pair of jeans, or as in this case, into a special belt buckle. There’s even a prototype version that’ll clip to the shoulder strap of a hydration pack or backpack. 
For more details, see Fix MFG’s website: https://fixmfg.com/product/wheelie-wrench/
It looks like they’ve worked hard to place that bag buckle exactly in a really bad place for crashing
Do like the belt though
The bag-tool isn’t a buckle, it’s a sliding strap-mount that you could put on any suitable strap – I’d have thought that it’d fit well on a shoulder strap and be both out of the way, yet handy. We’ll see if we can get one in to look at.
The belt plus multitool is $80 !!!! very cool, but very expensive
A Rapha belt is over £80 and whilst you may look like a tool whilst wearing one, it doesn’t provide any functional benefit when something besides your pants needs adjusting.
if you’ve got a bag why not have the tool in it?