For my last few weddings I have been using two Black Widow Holsters, one on my left and one on my right side. When paired with a mirrorless camera like the XPRO 2 or XT1 it makes so much sense as an alternative to a sling strap or a black widow strap.
The Spider Holster allows the camera to be down by your side, which gives you more freedom to move around. I do own several straps, Black Rapid, Money Maker etc.. but the Black Widow Holster has made a massive impact on how I work.
The holster uses your existing belt, you simply feed your belt through the back of the holster; and your done. There is a small pin which you attach to the bottom of your camera, which is what locks your camera into the holster; when you want to take the camera our of the holster, you simply lift up the red hand and pull the camera clear, when your done; simply push the pin past the lock and its all secure.
It really is a great little product, I have used this with a XT1 and the 50-140 zoom lens and it feels fine - they do a "PRO" version for larger DSLRs which isn't made from plastic.
Overall I'm pleased with the freedom it gives me and when used with Peak Design quick release straps it means I can go from the holster, to a single strap, to a hand holster in a matter of moments.
I will be doing a quick review of the Peak Design quick release system in a few weeks.