Above is a schematic for a very simple audible rocket locator. It's not real loud, but will help to locate that stray rocket in the grass, or crop field. If your high frequency hearing is good, you can hear it from over 100'.
Here are the parts I used, all from Radio Shack:
Red Blinking LED: 276-036
Piezo Buzzer: 273-060
16 volt, 220 uf electrolytic Capacitor
The blinking LED is the heart of the beeper, it makes the sound pitch vary with each blink of the LED. The LED has a frequency of about 2 Hz, (2 blinks per second) but will vary from .5 to 3 hz. The capacitor will charge between beeps and increase the sound level of the piezo buzzer. Play with different size capacitors to achieve the tone you like.
The LED is rated at 5 volts, but seems to work fine with 9 volts. Current consumption is very low, 5 mA at 12 volts. I suppose you could wire this to a timer, or even a deployment charge. But I think I will just power it from my deployment charge battery, and have it running when I turn the power on to my timer. It's not that annoying from a distance, and would be a nice indicator the timer is powered on. The piezo buzzer needs to be directed out of the rocket body. Such as a hole drilled through the body tube, or have the beeper deploy on the parachute recovery line.
This little beeper will really help if there is any amount of ground cover, or a rocket tangled in a tree. I like to watch my rocket launch from a marked location, then I use a pocket compass to get a heading of where the rocket landed. Jot down the heading in your notebook. Then you may pack up the launch site before heading out to find the rocket. For those who weren't Boy Scouts, when you start your trek to recover the rocket, don't hold the compass in your hand and try to navigate with it all the way. Take a sighting with your compass, and look for a landmark in the distance, then just walk to the landmark. You may use several landmark sightings with your compass as you go.
If you're in a crop over your head, you will of course need to use the compass constantly. In that case, make sure the compass is level. I "float" the compass by by turning it back and forth every few seconds, to make sure the needle isn't sticking. Walk as straight as possible, when you have to go around something make sure you return to your "line" on the other side of the obstruction. I have hundreds of hours experience navigating with a compass as a scuba instructor. You will be amazed at how accurate you will become with some experience.
For those rockets you lose sight of, I'm working a small FM tracking transmitter.