I have a drill/auger adapter, not the nimrod but the ice kicker, and it has a safety device so you don't lose your auger if the chuck comes loose. I've had mine for the past 2 ice seasons and it works awesome. The key is a 2 speed drill, on HIGH TORQUE and low speed. I have an 18v RIDGID drill that puts out about 450 in/lb of torque and it got me about 15 holes through 18" of ice at Okoboji last yr on one battery pack. One battery pack will last me about 25 holes on normal 7"-10" ice around Cedar Rapids. You CAN NOT use a regular Skil or Black and Decker drill, they will not work, as I found out on my trial run. You want a drill that can put out at least 300+ in/lbs of torque to work efficiently, teamed with no larger than a 6" mora or you get even better results on a 6" lazer. Also, you can justify a new drill, if you have to, by telling the wife you can use it around the house for maintenance...
Just do a search for Ice Kicker on ebay, the guy just made a new adapter with a chain drive that works with lower power drills and bigger augers, but it costs a lot more. These adapters are worth every penny with the right drill and a 5" - 6" auger.