If your needs are simple, the ml-l3 will just take the picture with no refocusing if you are set for bbf. (Thats on my d7200, but it should be the same on the 750.) All I need it to do is just snap the picture. I'm either shooting the moon or the bird feeder when I use the remote. I pre-focus with the bb and shoot as needed with the remote. The app is nice, but for what I do, the little remote is fine. My phone struggles to hold a charge a full day anyway so its best left in my pocket. You can get a knock-off ml-l3 for <$10 on Amazon or ebay if you want to try it.
I need to see if the app works on my tablet, that could be a handy setup. Kind of cool to touch the screen and focus.