It is a site that buys back old electronic items. Other similar sites include Gazelle.com and NextWorth.com.
I recently sent something in and they just arbitrarily gave me just 2/3 of the quoted value. No explanation. Just a check for a lesser amount.
In contrast, I have used Gazelle a couple of times and have had a great experience each time.
If others have used BuyMyTronics successfully then maybe you can post a positive comment to offer balance but I'm pretty annoyed they just gave me less money as if nothing happened.