Measuring the weight of a beehive

Hi
i working on similar project,i made scale for my beehive.I use arduino uno r3,gprs gsm shield sim 900,7.4V 1000mah lipo batery,DS1302 Real Time Clock,HX711 24 Precision AD Module Pressure Sensor Module Weighting Sensor, DHT-11 Digital Temperature and Humidity Sensor,and four cels from home body scale.
two times in day i recive sms with weight,humidity and temperature.i nead resolve problem with batery,does someone know how i can recive in sms how much i have power in batery,or alarm whan i hawe low power?
thank you for any help?
if you want i can post picture of my prototipe!