That site doesn't help author double-spends, but it will relay them, which OP originally asked for although he really wanted a friendly miner.

The site also has a record of the spends seen earlier (unlike blockchain)

http://respends.thinlink.com/tx/f34a12f0c153055ef8d9ca4c917861de9130651495c21b9eba792050a07bfa71
First seen in a block 12d after earlier tx 3d58d4417ce83003553c23c3c97cd942a6da8506864aa14af8dc963d618c1f9a

http://respends.thinlink.com/tx/604ff6cb6b605420139adfbf91fd31266cdafcb7ccd163cfbdbdf5a4fa7a1881
Seen on network 16h after earlier tx 333f27b77bea035e7e9a7a2551f55e395410945ebdc24d5c145b0cab0009d1cd.  Then confirmed.