Double or Nothing betting smart contract with Bitcoin

DoubleOrNothing.sol

contract Alarm {
    function deposit();
    function scheduleCall(address contractAddress, bytes4 abiSignature, bytes32
                          dataHash, uint targetBlock, uint8 gracePeriod);
}

contract BitcoinBridge {
    function queuePayment(bytes bitcoinAddress) returns(bool successful);
}

contract Etherdice {
    function bet(uint8 pick, bool isMirrored, uint8 die) returns (int);
}

contract DoubleOrNothing {
    Alarm public alarmClock = Alarm(0x07307d0b136a79bac718f43388aed706389c4588);
    BitcoinBridge public bitcoinBridge = BitcoinBridge(0x4d6387f3b967da39b11de111158d49754c31985d);
    Etherdice public etherdice = Etherdice(0x37005accab2a7807d8572902a172c2a325021910);

    bool public ongoingBet = false;
    uint public blockNumber;
    bytes public bitcoinAddress;

    function () {
        if (msg.sender == address(etherdice)) {
            // Etherdice is sending our winnings
            return;
        }

        if (ongoingBet || msg.value < 700 finney)
            throw;

        uint betAmount = msg.value - 200 finney;
        if (etherdice.bet.value(betAmount)(11, true, 1) == -1)
            throw;

        alarmClock.deposit.value(200 finney)();
        bytes4 sig = bytes4(sha3('alarm()'));
        bytes32 dataHash = sha3();
        uint targetBlock = block.number + 45;
        uint8 gracePeriod = 64;
        alarmClock.scheduleCall(this, sig, dataHash, targetBlock, gracePeriod);

        ongoingBet = true;
        blockNumber = block.number;
        bitcoinAddress = msg.data;
    }

    function alarm() {
        if (!ongoingBet)
            throw;

        if (block.number - blockNumber < 35)
            throw; // too early

        if (this.balance > 0)
            bitcoinBridge.queuePayment.value(this.balance)(bitcoinAddress);
        ongoingBet = false;
    }
}