As one of its daily deals, Amazon offers Prime members the Logitech M570 Wireless Trackball, model no. 910-001799, for $20.25 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $8.22.) That's tied with our July mention (which was a Prime Day deal) as the lowest total price we've seen for a new one. (It's the best deal now by $6.) Features include programmable buttons, 2.4GHz wireless with a 30-foot range, and up to 18 months of battery life. Deal ends today.