I use <a href="http:&#x2F;&#x2F;lessonslearned.org&#x2F;sniff" rel="nofollow">http:&#x2F;&#x2F;lessonslearned.org&#x2F;sniff</a> . I check it reflexively every so often, as Verizon has at least once re-enabled the super cookie after I had disabled it. That site checks for cookies from other carriers as well.