How can a Bitcoin Oracle ensure that the money can't be respent?
(elaborating on the comment I gave to the question)

You do this by wiring the funds to an address controlled by both you and an oracle (or a set of oracles). You do this by utilizing a bitcoin multisig address.

That way there's no way for you to move the funds away without oracle's permission, and there's no way for oracle to run away with funds.

As for preventing oracles from holding the transaction hostage, you can use distributed oracles - i.e. a set of independent oracles. So, to withdraw the funds you'd need a signature of both yourself, and say 8 out of 15 oracles. If you choose oracles wisely, the chance for them to collude and hold your funds for ransom should be minimal.

You can consult Orisi Whitepaper ( https://github.com/orisi/wiki/wiki/Orisi-White-Paper/ ) or website (oracles.li) or github repo (https://github.com/orisi/orisi) for more info.