One of the largest pending issues with modern day smartphones is the constantly dwindling battery life. More power, more capabilities, more sensors, more connectivity and more ways to use a smartphone can only result in one very important aspect of the smartphone taking a hit. That key aspect is, without a doubt, battery life.

Generally, I suggest people who need extra juice either carry a spare battery pack (I've been racking some of those up at CES this year), plug into any and all USB ports and outlets available, toggle connections on and off as needed, among other things. But one of the key advantages to carrying a BlackBerry, Android or Windows device is the ability to swap batteries out once the one inside dies. Simply pop the battery door off, remove the dead battery and replace it with a new, fully-charged cell. Millions of iPhone users, however, have been without replaceable batteries from day one – chances are that will stay the same for the foreseeable future.

While Apple may not officially be making the switch to removable batteries on their iDevices anytime soon, case manufacturers are. While on the show floor at CES today, I stumbled upon two very similar products that give iPhone users swappable batteries ... of a sort.

First up, I managed to score some hands-on time with a prototype of the upcoming Surface Plus and Convert Plus cases for the iPhone 4S. The core case is the Surface Plus, which, at a glance, looks much like any other battery pack case (like the mophie juice pack plus, for instance). And it is, for that matter. But it carries a unique perk – if you take the back cover off of the phone, you will notice that there is a removable 1,700 mAh battery pack. If your phone dies in Surface Plus, simply pop it off and insert a spare battery pack, much like you would do with an Android phone.

The Convert Plus is simply a rugged, two-layer case that goes over the Surface Plus. The inner layer is a thick silicon case, which then gets covered by a hard, flexible plastic shell. This particular case for the iPhone is a rather large and bulky solution, but at least customers have options and the two separate cases work so well together.

The other product I caught a glimpse of, in passing, was almost the exact same as Seidio's iPhone case, made by Incipio. It was a rather slim case (in comparison) that packs a nice, high capacity battery which can be removed and replaced with a spare. And for extra protection, a ruggedized, bumper-like case can be added to the inner case. I didn't catch the name of this particular case (it isn't the offGRID, but very similar), but it will set you back 100 big ones.

The pack made by Seidio, since it is a prototype after all, is not available, and I wasn't given any specific time frame for it to release. (I may have caught "middle of the year," as an estimated date, but I'm not 100 percent sure.) What Seidio did tell us, though, is that it will retail for less than $99.

I know, these are only cases, so they're not something to get overly excited for. But I really like the idea of removable batteries in an extended battery case, especially in press conferences. It keeps you from having to purchase two cases, but it requires you to disassemble the case entirely to swap batteries.

I tried my best to bag one of these cases, but that did not happen ... unfortunately. And I'm not sure that with all of the external battery chargers I have laying around and in my backpack, I don't need to spend an additional $100 on a case. Nonetheless, these are pretty cool concepts that fix one of the outlying issues with the iPhone.

What say you, iPhone mongers? Are extended battery packs still too large? Or do a couple giving the iPhone a swappable battery option make the added bulk worth it?