I found this via the Cycle chat forums. Looks neat! Original link below. My only fear is that I seem to be finding every more neat ideas for carrying ever more gear on the bikes. Not a good way to go!
At a glance Low-cost, tool storage tube that fits in a bottle cage
Tested by Jon Adams, tester for The Bike List
“Now this is a great idea. If your trusty bicycle repair kit is rattling around in a bum bag or bouncing around in a pannier, then it’d be a good idea to stick your multi-tool, tyre levers, spare tube, puncture kit and pair of pin-nose pliers elsewhere. But where do they go? In a barbag, so they can scratch your phone and bruise your banana, or in a jersey pocket so they can eat through the fabric or burrow into your back? Unless you have a specific pannier pocket or a saddle bag for the purpose, stowing tools is, quite frankly, a pain. Until, that is, you discover Pro Bike Gear’s Storage Bottle. It’s a simple plastic tube with a watertight, screw-on lid, and it has sculpted inserts shaped to fit into a standard bottle cage.
Most hardtails and road bikes have bosses for two cages (tourers often have three), and the majority of riders only need one water bottle. If that sounds like you, splash out a fiver on a second bottle cage, and then get one of these to put all those rattly tools in. The Storage Bottle comes in two sizes, and unless you’ve a reason not to, you may as well go for the larger 750ml, as cycling provides more than enough small bits and bobs to fill it. I put my spare tube in the bottom, then add the other essentials on top. There’s space for half a dozen zip ties, and a spare rear flasher and batteries, and I finish off with a couple of Bodyguard gloves so I can avoid getting my hands covered in crap when the chain falls off the rings (or the air falls out the tyres). The gloves also stop any rattles from the contents. Of course, you could cut down a standard bottle to achieve the same end, or fashion something ingenious from stuff you stumble across at the back of the garage, but why bother? For £6 (or just a fiver for the 500ml size) it’s all done for you. Love it!”