Out of the following choices I would buy..DTS TrackerOrtovox m2Ortovox X1Mammut Barryvox Mammut Barryvoxhttp://www.barryvox.com/productfamily/mammut/index_e.htmlTechnical databattery life: 200 hours SEND minimum, usually more than 300 hours operating frequency: 457 kHz maximum range: approx. 60m batteries: 3 alkalinemagnesium cells, size AAA dimensions: 108 x 68 x 25 mm weight: 170gr (including batteries) Ortovox X1http://www.ortovox.com/eng/start.htmTECHNICAL DATAFUNCTIONS: digital + analog (2 antennae) CASING: anatomically shaped, waterproof, secure and rugged according to the European standard EN 300 718 DIMENSIONS: 120 x 80 x 20 mm TRANSMITTER AND RECEIVER FREQUENCY: 457 kHz RANGE: up to 80 m SEARCH STRIP WIDTH: up to 40 m TEMPERATURE: -30° to +50° C BATTERIES: 2 LR6 Mignon 1.5V E91 AM3 AA WORKING LIFE: TRANSMITTING: approx. 300 hours RECEIVING: approx. 40 hours WEIGHT: approx. 247 g (batteries and body belt included) Tracker DTS (BCA)http://www.bcaccess.com/bcaproducts/tracker/tracker_home.phpFrequency: 457 kHzBatteries: three AAA alkalinesBattery life: minimum 1 hour in search mode after 200 hours intransmit mode (approximately 250 hours in transmit only or 50 hours in search only)Weight: 10.5 ounces (298 grams), including strap and batteries; 8.3 ounces (200 grams) without strap and batteries.Size: 5-3/4” x 3-1/4” x 1-1/4” (14cm x 8cm x 3cm)Limited 3-year warrantyTracker's maximum receive range of 50 meters Ortovox M2http://www.ortovox.com/eng/start.htmTECHNICAL DATAFUNCTIONS: digital + analog HOUSING: anatomically shaped, waterproof, secure and rugged according to EN 300 718 DIMENSIONS: 145 x 62 x 25 mm TRANSMITTER AND RECEIVER FREQUENCY: 457 kHz RANGE: up to 80 m SEARCH STRIP WIDTH: up to 40 m TEMPERATURE: -30° to +50° C BATTERIES: 2 x LR6 Mignon 1,5 V E91 AM3 AA (no rechargeables) = 2 "AA" batteries BATTERY LIFE: TRANSMITTING: approx. 300 hours RECEIVING: approx. 40 hours WEIGHT: approx. 230 G, incl. batteries