KS, you ask good questions
A kick is an electronic "addon" that goes between the battery and the positive contact. It "regulates" the voltage so that there's no "drop off" in performance as the battery slowly drains down from its (charged) 4.2v down to around 3.5(ish....if I recall correctly). It requires some modification to the REO, but Robert is working on a mod that is "kick ready", i.e., it will come with a spacer that allows the mod to function as purely mechanical (like the current REOs), and which can be removed to insert a kick. If the kick fails, the spacer can be put back in to run pure mechanical while you wait for a new kick to arrive in the mail.
There are numerous articles both here on ECF and on the candlepower forums about battery safety, that, trust me, will go into way more detail than you need, but they're worth a scan anyway. The basics are really just common sense. Use a quality charger, use safe chemistry batteries (IMR), periodically check them coming off the charger to ensure that they are charging properly (should be about 4.1 or 4.2 for an 18650 AW IMR). Change them out at a frequency that keeps them above about 3.5 (the vapor/flavor will taper off around 3.9 anyway). Do that, at first, by checking them with a multimeter throughout the day, for a "moderate" vaper like myself, that turns out to be *roughly* fresh battery (1600 mAH AW IMR) in the morning, fresh battery around 6:00 pm. After you know what your "schedule" is, just check them occasionally to make sure they're staying within range.
The rest is normal battery safety. Never leave them where subjected to temperature extremes. Never charge them unattended, always on a flame resistant surface. Never carry them in a way that would allow them to short (keys in purse, coins coming in contact, etc.) A battery case is designed with this in mind and they're cheap and quite functional. If a battery is dropped or damaged in some way, test it before use, or, if in any doubt, replace it.
That's the crux of it, if I've missed anything important, hopefully someone will chime in shortly.
