Seeed Studio is working on a probe cable for the Open Logic Sniffer. We’ll give you an update as soon as we hear more.
You can try building your own cable with some cheap probes from Deal Extreme (~$3 for 10). The trick will be finding a 1×9 row connector, if you know of any sources please share them in the comments.
The Open Logic Sniffer is currently available for preorder at Seeed Studio for $45, including worldwide shipping.