Do braces/ medical tubing etc do anything in fallout 3?

Most of those items you mentioned actually are components of the various weapons you will be able to build once you obtain their schematics from various traders as you proceed through the game. Moira sells the Rock-It Launcher Schematics from the beginning and will either sell you or you have to earn the Bottlecap Mine Schematics from her as well. Later on there's the Railway Rifle, the dart gun, nuka grenades, and the Shiskebob, each of which would be the ultimate weapon for an expert in its weapon type. By the time you purchase the schematics you can either buy the items you need back from the traders or at least you'll know what to look for. It's better to get the cash now and buy better weapons, armor, upgrades and medicines than hold onto everything in case you'll need it later.