I bought these DCI Keychain Tools screwdrivers 5 years ago through Amazon.
http://www.amazon.com/DCI-26829-Travel-Tools-Keychain/dp/B0051V4XV0/ref=sr_1_1?ie=UTF8&sr=8-1&keywords=B0051V4XV0It wasn't obvious from the web page photos that the screwdriver handles are smaller than those on ordinary keys. The "handles" on the flat and Phillips drivers are different sizes, but both are way too small to provide enough torque to drive all but the loosest of screws. You can apply more torque by using your key ring as a lever, but that arrangement is unwieldy and you risk bending your split ring.
The metalwork finishing is crude.
On the plus side, the 1/4 inch hex shafts can be filed down a little to fit through the hex hole in a key chain pry tool to gain extra torque if you have such a tool.
I didn't find this product useful due to the limited power so it stays at home in a drawer instead of on my keychain.