What's the easiest way to someone to double-spend 0-confirmation transactions? I heard there is a desktop app today that 'easily double spends 0-conf tx'. Which is it? Is anyone working on a mobile version of this app?
Peter Todd wrote [Replace-By-Fee Tools](https://github.com/petertodd/replace-by-fee-tools
)


  Basic usage:
  
  ./double-spend.py &lt;address&gt; &lt;amount&gt;
  
  Creates two transactions in succession. The first pays the specified
  amount to the specified address. The second double-spends that
  transaction with a transaction with higher fees, paying only the
  change address. In addition you can optionally specify that the first
  transaction additional OP-RETURN, multisig, and "blacklisted" address
  outputs. Some miners won't accept transactions with these output
  types; those miners will accept the second double-spend transaction,
  helping you achieve a succesful double-spend.