I bought a yongnuo YN-460II flash to use as a wireless flash for my nex-5. It works somehow but absolutely unreliable outside, especially under bright sun.
I made this fiber optic cable from an unjacketed 1mm diameter fiber to trigger the external flash. The first version was OK, but didn’t work under direct sun due to the light leakage. The rubber band used for the attachment also covered the back buttons.
In the second version I used a plastic foam sheet to cover the IR sensor of the flash and attach the fiber to the strobe. The other end of the fiber was glued to a LEGO brick an was attached with a cardboard box to the on-board flash:
Now it works flawless even under the brightest sun. One recent example taken with this system:
More details are on my blog: