Rebooting your iPhone or iPad is often viewed as a big no-no in the jailbreak community, especially since all modern jailbreaks are either semi-tethered or semi-untethered, which means having to re-run the tool after a reboot to return to a jailbroken state.
In some cases, a reboot may seem unavoidable because your handset’s battery runs out before you can get to a charger. Fortunately, a newly released and free jailbreak tweak called Sentinel by iOS developer MegaDev tries to prevent this from happening by putting your handset into an hibernation-like state when the battery gets too low so that you have more time to get to a charger before a forced shutdown becomes inevitable.