Using Ethereum as an Event Store. See https://forum.ethereum.org/discussion/3243/events-in-solidity-using-blockchain-as-eventstore#latest

eth-events.js

//Creating a Mongo collection to keep track of events
EthEvents = new Mongo.Collection('ethEvents');
EthEvents.attachSchema(new SimpleSchema({
    contractAddress: {
        type: String,
        index: true
    },
    eventName: {
        type: String,
        index: true
    },
    blockNumber: {
        type: Number,
        min: 0
    }
}));

EthEvents.watchEvent = function (contractInstance, eventName, onEvent) {
    if (!Contracts.useWeb3) {
        return;
    }
    //What's the blocknumber of the event we've received before the restart?
    var previous = EthEvents.findOne({
        contractAddress: contractInstance.address,
        eventName: eventName
    });
    //TODO handle forks
    var fromBlock = previous ? previous.blockNumber + 1 : 0;
    var options = {
        'address': contractInstance.address,
        'fromBlock': fromBlock
    };
    var updateFromBlock = function (err, event) {
        //First update mongodb, then execute onEvent handler. Should mongo crash or fail, at least we re-receive the latest event
        EthEvents.upsert({
            contractAddress: contractInstance.address,
            eventName: eventName
        }, {
            $set: {
                blockNumber: event.blockNumber
            }
        }, function (dbError) {
            if (!dbError) {
                onEvent(err, event);
            };
        });
    };
    var contractEvent = contractInstance[eventName];
    contractEvent({}, options).watch(Meteor.bindEnvironment(updateFromBlock));
    console.log("init filter event", eventName, "of contract", contractInstance.address, "from block", fromBlock);
};

//TODO add proper error handling. Do something with success and failure returns in the Ethereum contracts also
EthEvents.handleCall = function (onSuccess) {
    return Meteor.bindEnvironment(function (e, tx) {
        if (!e) {
            onSuccess(tx);
        } else {
            console.log("Failed to call Ethereum", e);
        }
    });
};

//You can watch events using the following code:
/*
EthEvents.watchEvent(MyContracABI, "<EventName>", myHandler);
MyContractABI is an contract instance, Eventname is of course the name of the even. MyHandler is a simple function with params (err, event) to handle the event.
*/