iPhone uploading binary file to Node.js server (Using express, mongoDB, and mongoose)

sorry, very new to Node.js here. I am having trouble getting my head around a good strategy to upload files from an iphone client into a node.js server and storing it on the server side.

For now, I can accept a binary file on the server and save it to the filesystem with the following code:

app.post('/upload', function(req, res){

    // get the temporary location of the file
    var tmp_path = req.files.pic.path;
    // set where the file should actually exists - in this case it is in the "images" directory
    var target_path = './uploads/' + req.files.pic.name;
    // move the file from the temporary location to the intended location
    fs.rename(tmp_path, target_path, function(err) {
        if (err) throw err;
        // delete the temporary file, so that the explicitly set temporary upload dir does not get filled with unwanted files
        fs.unlink(tmp_path, function() {
            if (err) throw err;
            res.send('File uploaded to: ' + target_path + ' - ' + req.files.pic.size + ' bytes');
        });
    });

    console.log(req.files.pic.name);
    res.send('DONE', 200);
    res.end();
});

With this code, I first accept a multipart form upload of a jpeg from the iphone into the /tmp directory, then I rename and move the file to the ./uploads directory. My problem is how to save this file into the DB.

From what I've read, I have three choices (I think!)

1. Save the files to some upload directory and store the local path into the mongodb for later access
2. Save the file itself into MongoDb with a Buffer
3. Use grid-fs to save the file.

I have been trying #3 using this module I found called gridfs-stream (Since I am using mongoose), but I really don't understand the source code in the package.

My question is a two-parter: Among the 3 choices above, would #3 indeed be the way to go? If so, I really need some help on understanding how to use gridfs-stream.

I know the following code is wrong, but this is my attempt thus far to see if I can slot it into my existing upload code:

app.post('/upload', function(req, res){

    // get the temporary location of the file
    var tmp_path = req.files.pic.path;
    // set where the file should actually exists - in this case it is in the "images" directory
    var target_path = './uploads/' + req.files.pic.name;
    // move the file from the temporary location to the intended location
    fs.rename(tmp_path, target_path, function(err) {
        if (err) throw err;

        var conn = mongoose.createConnection('localhost', 'myahkvoicedb');

        conn.once('open', function () {
            var gfs = Grid(conn.db, mongoose.mongo);

            // all set!
            var writestream = gfs.createWriteStream('req.files.pic.name');
            fs.createReadStream('./uploads/').pipe(writestream);

            /* // APP CRASHES HERE WITH THE FOLLOWING:
            stream.js:81
            throw er; // Unhandled stream error in pipe.
            ^
            Error: EISDIR, read
            */
        })


        // delete the temporary file, so that the explicitly set temporary upload dir does not get filled with unwanted files
        fs.unlink(tmp_path, function() {
            if (err) throw err;
            res.send('File uploaded to: ' + target_path + ' - ' + req.files.pic.size + ' bytes');
        });
    });

    console.log(req.files.pic.name);
    res.send('DONE', 200);
    res.end();
});

Any help would be appreciated. Thank you!