Also I love my new Tilt, which monitors SG the whole way, though it is a bit finicky.
What is finicky about the Tilt? I am an extreme tightwad but if I was going to splurge on a brewing accessory this might be the one as it seems to solve all the above mentioned issues with refractometers and hydrometers.
The Tilt requires Bluetooth technology and/or faulty phone app... which for some reason tends to get disconnected every 2-6 hours, at least that's been my experience but I know for certain I'm not the only one, I've heard reports of same or similar from several others. This means we need to manually unclick and re-click the Bluetooth connection every so often to re-establish connection. Not a real big deal unless you're going to be away for a whole day and REALLY NEED to know the exact SG at all times..... personally I don't sweat it too much, I just enjoy seeing the trend and knowing when to change temperature or dry hop or whatever. On the other hand, you're about equally likely to be one of the lucky people who never have this problem. Flip a coin. Maybe you'll be lucky. I'm never so lucky.
Another thing is that for good accuracy, it needs to be calibrated, and re-calibrated, and re-re-calibrated, prior to every use, IF you want it to be very accurate within 0.001-0.002. If that level of accuracy isn't important, great, skip the extra calibration steps and you'll still be happy. But if you're retentive like I am, the extra calibration necessary is a little bit of a pain. Personally I'm pretty content (so far, anyway) to deal with it because to me it's worth the little extra effort.
The other touchy thing with Tilt is that after it has krausen and/or hops stuck to it, it tends to read low by approximately 0.002 or thereabouts (in my experience). But as long as you know this, you can easily correct for it at the end of fermentation. You can gently shake the fermenter to get some of it off, or just live with a reading that's a little off.
Alternatively........ I really really REALLY love my refractometer, now that I know how to use it correctly. See link from my previous post above. It's friggin awesome, and accurate within 0.001-0.002 every time without a lot of extra calibration steps. A couple drops and you're good to go -- how easy is that! And cheap!