It uses the bike battery but if thats disconnected it switches to its own internal one, theory is on lowest settings the internal one lasts 24 hours....But with the settings I use (more power hungry) it lasts about 4.5 hours on its own battery Also worth mentioning its compatible with both 12 & 24 volts Its never affected my bike battery, even though basic settings its actually a silent alarm system that actually texts you If someone touches your bike Cant help with SIM question as I use a £5 GiffGaff one with 500 txts and 100MB ...you will typically only use about 2-4 Mb a month You use either txt reports, or use their free 1 year GPS tracking site....which reports everything I wont be renewing my membership because it records speed, miles,distance, even when the engine is ON/OFF although if its nicked you can literally track a moving bike down to 5 meters For the price it is great value EDIT: the companys after sales is of the highest caliper and they will bend over backwards to help ....I am impressed with that they will even set it up for you if you give them access