Bicycling Magazine has an article on the new SRAM 1x groupset in the September 2015 issue. This is not the same as a fixed speed bike. The "1x" refers to one chainring. You still get a cassette on the back with plenty of gears, so this is not a single speed. But perhaps it is close enough for you -- an alternative to a true single speed?
The SRAM 1x gets tested by different staff members. Note that the testers are extremely fit, experienced cyclists. Fit. Strong. Fit. Thousands of feet in elevation astride an 1x might not bother them -- but at this moment in my life it would bother me. So it is important to understand who the testers are and what their viewpoints are. My personal assessment of my own riding skills on a 1x is "Maryland Weakling". The magazine staff also conducted tests on extremely good bikes, not on iron tubes that got welded together by the local home improvement guy which were then awarded the generous label of "bicycle".
Bob