From manufacturer's site: 

A peanut-sized altimeter with super-sized features!  This tiny, easy to use altimeter audibly reports your rocket's peak altitude and maximum velocity after flight via a sequence of beeps.  A post-flight warbling siren sound makes finding small rockets in tall grass easier.

The Pnut collects flight data (altitude, temperature, and battery voltage) at a rate of 20 samples per second throughout the flight and stores them for later download to a computer.  It retains data from the most recent 31 flights (up to 9 minutes per flight) even with power removed.  The optional DT3U data transfer kit includes software for graphing and printing a wide range of characteristics including altitude, velocity, and more.

Despite its small size and low price, the Pnut is capable of recording flights of up to 100,000 foot altitude with industry-leading precision and accuracy.

A built-in Lithium Polymer rechargeable battery will run the Pnut for up to 100 hours between charges.