When it comes to sewing and other highly intricate crafts, the devil is in the details. You need to see clearly in order to add that perfect yet microscopic touch, and more often than not, you're stooped over whatever your working on, blocking out your own light. Solve both problems by investing in a good lighted magnifier. They can help you get a clearer picture of what your working on: at least until humans figure out how to get zoom vision.
Hobby Horse
A lighted magnifier can serve all kinds of hobbies, not least of which is sewing. Any craft that requires fine detail work can benefit from the use of a lighted magnifier, but sewing requires a steady hand and a good sense of timing and perspective to get a project done. Whether you're fixing a pocket by hand, putting a dress pattern together or adding some beading to a blouse, you need to have a good view of what you're working on. Otherwise, you'll end up with warped Gordon Gartrells and a large scrap pile. Other hobbies, like wood working, sculpture and jewelry-making might similarly call for a lighted magnifier.
Varieties
Lighted magnifiers come in a few varieties, any of which might suit your hobby activities. A lighted version of the traditional magnifying glass is best for a post-production quality check, giving you the range to fully inspect your work, or enjoy the details of someone else's hard labor. Pocket magnifiers with lights are also good in this respect, though their smaller stature may result in a reduced view. On the plus side, they're portable, and perfect for hobby classes. Magnifying loupes offer the same benefits, with the added benefit of being as big as your eye can see.
Lighted magnifying visors are a great hands-free option that's better for using while you're on the job, so to speak. You can work with out stopping to check out the finer details. Neck hanging lighted magnifiers can work the same way, though the strap is mostly to keep it handy rather than to help aid your view. You can also invest in an magnifying lamp; they're expensive but worth it for long term, at home use.