if you mean the XRAY active diff [link=http://www.teamxray.com/teamxray/news/newsdesc.php?news_id=1305&kategoria=1305&Xnet_Sess ion=adc7d9c4b824ce0cd1fa9a38c526b791]SHOWN HERE[/link] then yes they do make a diff that locks up on power
so do BBF, who have made Tactyl diffs for most poular cars for a few years now as have Fioroni with their Tractive IV diffs

basically these are powerlock or varilock diffs that just lock up under power but run fairly freely off power, the locking action is tunable by the use of ramps of different angles which is explained at the bottom of the XRAY link i posted above

however, they are NOT 1way diffs like the original poster asked for but they are probably the closest thing in on power operation & feel available to us at the moment

a good page explaining varilock diff operation [link=http://www.variloc.com/variloc_theory.htm]HERE[/link] [:-]