You're a lucky man. My wife is mad at me now because I "over-enjoy my hobbies." (referring to the fact that I keep an eye out for squirrels during dinner) She was going to watch our daughter tomorrow morning, so I can go shoot the field target match, but she just canceled last minute.
She said she's not really interested in it, I asked her to try a little more; try some plinking. She won't. She's a runner, I even offered to run an hour for every hour she shoots with me, that way we could spend time together, even if it is not our individual favorite hobbies.
As for your original question, there are all these complex methods. I say keep it simple. Get an inexpensive spotting scope and an inexpensive rangefinder. The nice thing about these is that you can use them anywhere, not just at home. Also, they're very little work to set up, compared to things buried in the ground.
I also use natural landmarks. For instance, from the area I shoot from on my patio to the base of the mulberry tree, underneath the bird feeder is almost exactly 10 yards. From the shooting area to the back of the lawn where the stump is set up is 35 yards. I've also found the yardage markings on my scope objective to be fairly accurate. If they're off by a couple yards either way, so what? Pellets don't drop THAT fast, right?
I send em running down range when I can't see it. It's been working rather well for me. You should get some. There kinda expensive though. 
