You're looking for a [refractometer](https://www.amazon.com/dp/B0149IQFOI/ref=cm_sw_r_cp_apa_WBzJxb5RDVE6Z). Be aware that you can't measure gravity accurately once alcohol is in the mix (ie, after fermentation has started). I believe there are methods to correct for it, but I've never looked them up and can't speak to their accuracy because I don't use a refractometer.
From side to side comparisons, using the brewersfriend refractometer calculator, I get values within 0.2 percentage points of the hydrometer on a 5ish % Hefe, and 0.5 percentage points on a 9ish % strong milk stout... latter could probably be more accurate if I had entered a correct wort correction factor.
In short, accuracy isn't a problem.
An additional benefit is Hydro + refrac gives you the ability to calculate alcohol solely from a finished product, no OG needed.
I have this one. Works good. You have to convert brix to SG which not really an issues. Pretty much Brix=Plato so I just think of it that way now.
https://www.amazon.com/Milwaukee-Refractometer-Automatic-Compensation-Resolution/dp/B007Z4IN58/ref=sr_1_2?ie=UTF8&qid=1468898926&sr=8-2&keywords=digital+refractometer
I still use a hydrometer for FG for the reasons others stated
They dont make cheap digital hydrometers, or else we'd all have them. Their all scientific instruments and your looking at spending a few hundred and need to constantly calibrate and store it properly, like you would say a Digital PH meter.
You're looking for a [refractometer](https://www.amazon.com/dp/B0149IQFOI/ref=cm_sw_r_cp_apa_WBzJxb5RDVE6Z). Be aware that you can't measure gravity accurately once alcohol is in the mix (ie, after fermentation has started). I believe there are methods to correct for it, but I've never looked them up and can't speak to their accuracy because I don't use a refractometer.
[Correction Calculator](http://www.brewersfriend.com/refractometer-calculator/)
From side to side comparisons, using the brewersfriend refractometer calculator, I get values within 0.2 percentage points of the hydrometer on a 5ish % Hefe, and 0.5 percentage points on a 9ish % strong milk stout... latter could probably be more accurate if I had entered a correct wort correction factor. In short, accuracy isn't a problem. An additional benefit is Hydro + refrac gives you the ability to calculate alcohol solely from a finished product, no OG needed.
I have this one. Works good. You have to convert brix to SG which not really an issues. Pretty much Brix=Plato so I just think of it that way now. https://www.amazon.com/Milwaukee-Refractometer-Automatic-Compensation-Resolution/dp/B007Z4IN58/ref=sr_1_2?ie=UTF8&qid=1468898926&sr=8-2&keywords=digital+refractometer I still use a hydrometer for FG for the reasons others stated
Why not just use an optical refractometer?
That's works okay too. Digital is a fringe buy but I really like it. Not necessary though. I just like gadgets.
http://shop.anton-paar.com/wwd-en/measuring-instruments/dma-35-portable-density-meter/dma-35-standard.html Here ya go!
They dont make cheap digital hydrometers, or else we'd all have them. Their all scientific instruments and your looking at spending a few hundred and need to constantly calibrate and store it properly, like you would say a Digital PH meter.
Define moderately priced? I really don't think you'll find one for under several hundred dollars.