Independent Research and institutional review boards?
This issue actually got some press recently with the case of uBiome, a citizen science startup that raised over $350,000 in crowdfunding.

This startup received a lot of negative attention for not getting IRB approval before raising the money. You can read some of this criticism here, here, and here. 

A statement from the founders of uBiome says they were advised that they don't legally require IRB approval if they aren't receiving federal funding, don't plan to publish, and don't plan to apply for FDA (U.S. Food and Drug Administration) approval:


  Before we started our crowdfunding campaign, we consulted with our advisors at QB3, the startup incubator at UCSF, and the lawyers they provided us. We were informed (correctly) that IRBs are only required for federally funded projects, clinical trials, and those who seek publication in peer-reviewed journals. That’s right — projects that don’t want federal money, FDA approval, or to publish in traditional journals require no ethical review at all as far as we know. (No, that doesn’t sound like a great system to us either.)


In the end, they went through a private IRB firm (Wikipedia says it was this one) and got their protocols approved. The founders say: 


  This is the same institution that works with academic IRBs that need to coordinate multi-site studies, as well as private firms such as 23andme and pharmaceutical companies doing clinical trials. 


This incident raises the question of what you plan to do with your independent research (assuming the kind of research you are doing is generally subject to IRB oversight):


If you plan to publish your research in a traditional peer-reviewed journal, you will usually need an IRB review
If you plan to develop pharmaceuticals that will require FDA approval, you will need IRB review
If you plan to get federal funding for your work, you will need IRB review. If you plan to get other funding for your work, it'll be hard to get without IRB review.
If you plan to create a startup around your research, you may not require IRB review, but not having it can engender quite a bit of criticism (as per uBiome's story)