go Ethereum console, start miner only when there's tx in pool & confirm. https://ethereum.stackexchange.com/a/3152 https://ethereum.stackexchange.com/questions/2531/common-useful-javascript-snippets-for-geth

smartMiner.js

var confirmBlocks =13;
var counter = confirmBlocks;

function checkWork(chx) {
    if(chx == 0 && counter > 0){ //countdown
        counter--;
        return startMiner(counter);
    }else if(chx == 1 && eth.getBlock("pending").transactions.length > 0){ //TX in POOL
        counter = confirmBlocks;
        return startMiner(counter);
    }else{
        return stopMiner(counter);
    }
}

function startMiner(counter){
    if (eth.mining) return true;
    console.log("__Mining Started_"+counter);
    return miner.start();;
}
function stopMiner(counter){
    if (!eth.mining) return true;
    console.log("__Mining stopped_"+counter);
    return miner.stop();
}

eth.filter("latest", function(err, block) { 
  checkWork(0); 
});
eth.filter("pending", function(err, block) { 
  checkWork(1); 
});
checkWork(0);