I'm not familiar with a tool specifically for breaking secure lug nuts, but check this out:
http://www.harborfreight.com/cpi/cta...emnumber=98801
It says the larger one works on nuts up to 7/8".
Also, there's always the dremel, or its big brother the pneumatic die grinder to cut it off...or an angle grinder, for that matter, which could also be used to create wrench flats.
It may also be possible to drill two holes and use a really beefy (pardon the pun) pin spanner, but I doubt you can find one tough enough.
Look for stamped-in printing on it. There may be a number, which you can use to have the manufacturer supply you with a new key. Hopefully there's a manufacturer name there too, else you have to start guessing...
Edit: While googling to find the tool, I came across a better idea: Weld a regular nut to it and use a regular lug wrench.