If your not testing your wan (ISP) connection, all you need to use flent is a netperf server "netserver" and the ability to respond to pings (an irtt client/server is recommended).
It is possible to install netperf (with a netserver) via opkg on your openwrt wifi AP opkg update; opkg install netperf. You will need to keep an eye on your AP cpu usage to make sure your not making observations that are limited by the AP cpu.
You can record the AP cpu (plus other AP stats if your interested) via flent if you also install opkg install flent-tools. To get the stats I use a passwordless ssh key on the AP and then include in the flent command line --test-parameter=cpu_stats_hosts=<AP-host>.
Again, I've tried both a netperf server and an irrt server running from a osx box - I don't recommend you do this except to convice yourself its not a good idea (but running flent from osx out to a non osx server may still be useful). Linux netperf/irtt servers can work (just look out for the wifi powersave feature mentioned above).
Keep in mind, ATF (and i suspect AQL) have the most impact when streaming from your AP to your clients. Streaming from you client to your AP will not be as informative.
HTH