Is it possible to make a term contract with multisig/P2SH ?
I'll move 10 Bitcoins from my address to another, and I set 20 confirmations.
If no one will give the remain sign to move them to the bitcoin address or to move back to me on next 20 confirmations ... these 10 Bitcoin will lose their owner and they will be able to be mined again from miners.
Me and the other receiver-address-owner must be able to see the remaining confirmations, he must be able to see that there is a deadline and when it will expiry.
You could send the coins with the output requiring 2-of-2 signatures to spend, yours and the receivers. Then you and the receiver both sign a transaction with a 0 output (or no output? is that legal? not sure how else this would work and affect potential pruning in the future) and all the money going to fees with an nLockTime of either a block number or a time in the future. This spends that entire output to fees.
After that, it's up to you and the receiver to negotiate a transaction favorable to you both before the deadline. However, the receiver doesn't really have any motivation to cooperate with you as you'd be the only one losing money and she'd just not be gaining any.