What about enlarge the size of your mobile phone screen to watch videos ?
here a simple yet amazing trick
1 - Obtain a Fresnel lens like one of these from eBay or other retailer.
2- Make a stand for the lens. This can be as simple as cutting slots in two blocks of rubber, foam or wood.
3- Stand the lens vertically and prop up your cell phone behind it.
4- Adjust the distance between the two until the magnification is to your liking.