This is so useful I bought one myself. It's a waterproof phone, PTT cellular radio, camera, GPS, web browser and location tracker and you won't be afraid to take it out in the field with you. Comes with a handy belt clip.
The Telo TE580 & TE580 Plus are extremely useful two-way 'radios' using a cellular connection to queue, send and receive voice comms across any distance, so long as each handset can connect with the cellular network periodically.
A really useful feature is that when teamed up with ZelloWorks, a real-time location feature is available, which is especially useful for monitoring lone workers in remote locations. Ecologists and other field-based scientists can often find themselves alone and having a TE580 can enable them to communicate easily with fellow workers, as well as allowing an overview of individuals' locations on a live map, back at the office or on a remote computer (requires ZelloWorks).
Importantly, these have a much better antenna than mobile phones, so can connect when phones cannot. It can also be used for making phone calls.
Model: TE580 / TE580 Plus
Type: GSM/3G/4G/LTE with Bluetooth and WiFi
Operating System: Android 5.1 (8.1 for Plus)
Audio: 2.0W power
Range: Global (with cellular connection)
Waterproof: IP67 (includes immersion of 1m for 30 minutes
Location Service: GPS/GLONASS/AGPS
WiFi: 2.4GHz & 5GHz
Camera: 8MP rear, 2MP front, flash
Screen: 2.4" capacitive (3.1" for Plus), touch screen
Port: Micro USB
Interface: M6 interface for remote speaker microphone, earpiece, external camera
Sensors: G-sensor+acceleration sensor, Proximity sensor, light sensor, e-compass
Web: Android supported web browser
Buttons: PTT key, Volume up/down, Menu/Back/Home, Channel+/-, Mute, SOS, Power
Durability: IP67, drop test 1.5m
Operating temperature: -20 C - 60 C, Humidity: 20 - 90%
Memory: RAM+ROM = 1GB+8GB; SD card 32GB
Battery: 3,600mAh removable
Size (mm): 119.5 x 61.5 x 26.5 mm (119.5 x 61.5 x 23.5 mm for Plus)
Weight (g): Less than 205g (198g for Plus)
£300 inc UK delivery & VAT
£330 inc UK delivery & VAT