$ node walletmon.js

var http = require('http');
var currency = 'USD';
var addresses = [
    '17xxoEVft19Rg2V4vqop92Az7Hp7vbtttV',
    '13kEG7RopYCSqgG1T1YsULpTQx5sW1PLTy',
    '1MWYjCaMunK2rERswXxiNTV641y23k38BS',
    '1GaLzoNQbuJB4hDgY4YBgvjxzPqHkCebgj',
];

function getReceived(address, callback) {
    getData(address, 'received', callback);
}

function getSent(address, callback) {
    getData(address, 'sent', callback);
}

function getData(address, method, callback) {
    var options = {
      host: 'blockexplorer.com',
      port: 80,
      path: '/q/get'+method+'byaddress/'+address,
    };
    http.get(options, function(res) {
        var answer = '';
        res.on('data', function (chunk) {
            answer += chunk;
        });
        res.on('end', function (chunk) {
            if(chunk) answer += chunk;
            callback(answer);
        });
    });
}

function getWeightedPrices(callback) {
    var options = {
      host: 'bitcoincharts.com',
      port: 80,
      path: '/t/weighted_prices.json',
    };

    http.get(options, function(res) {
    var answer = '';
            res.on('data', function (chunk) {
            answer += chunk;
        });
        res.on('end', function (chunk) {
            if(chunk) answer += chunk;
            callback(JSON.parse(answer));
        });
    });
}

function fetch(index, callback) {
    getReceived(addresses[index], function(received) {
        var bal = Math.round(received * 1e8);
        getSent(addresses[index], function(sent) {
            bal -= Math.round(sent * 1e8);
            console.log(addresses[index]+' received: '+received+', sent: '+sent+', bal: '+(bal/1e8));
            callback(bal);
        });
    });
}

function main() {
    var total=0;
    var count=addresses.length;
    for(i=0; i<addresses.length; i++) {
        (function(index) {
            fetch(index, function(bal) {
                total += bal;
                count--;
                if(count == 0) {
                    getWeightedPrices(function(prices) {
                        var p24h = Math.round(total * prices[currency]['24h'] / 1e6) / 1e2;
                        var p7d = Math.round(total * prices[currency]['7d'] / 1e6) / 1e2;
                        var p30d = Math.round(total * prices[currency]['30d'] / 1e6) /1e2;
                        console.log('');
                        console.log('Total: '+ (total / 1e8) + ' BTC ('+addresses.length+' addresses)');
                        console.log('USD: '+p24h+'(24h), '+p7d+'(7d) '+p30d+'(30d)');
                    })
                }
            });
        })(i);
    }
}

main();