A pair of Twofish blocks + a Velcro strap. Buy the inline channel versions (Bikeblock) or the cross channel versions (Lockblock) depending on how you choose to mount the lock. The megablock + a additional Velcro strap might work too.
http://www.twofish.biz/bike.html
I have seen complaints about both current OnGuard and Kryptonite lock hangers as NWAS.
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Gear Hubs Owned: Rohloff disc brake, SRAM iM9 disc brake, SRAM P5 freewheel, Sachs Torpedo 3 speed freewheel, NuVinci CVT, Shimano Alfine SG S-501, Sturmey Archer S5-2 Alloy. Other: 83 Colnago Super Record, Univega Via De Oro
Visit and join the Yahoo Geared Hub Bikes group for support and links.
http://groups.yahoo.com/group/Geared_hub_bikes/