More than 400 million iOS devices are currently in circulation, and the range of accessories for designed for iPhones is constantly expanding.

With the holiday shopping frenzy just around the corner, retailers are pulling out all of the stops to lure iDevice fans. iDevice accessories. But before you head to your favorite store, take a look at the top iPhone accessories that have become popular among iPhone fans:

•  Opena - iPhone Bottle Opener

Everyone is going to at least one party during the holidays, and everyone has at least one friend that has everything, making is very difficult to come up with the right gift. The Opena iPhone bottle opener is basically a protective hard case enclosing a slide-out bottle opener. Combining protection with functionality, this iPhone accessory is expected to be a big hit this holiday season. It comes in Black and White color options, is compatible with the iPhone 4 and 4S, and comes with a $39.95. An iPhone 5 model is in the works as well. The Opena iPhone bottle opener is available for purchase on Opena's Web site.

•  Holda - iPhone Wallet Case

The Holda wallet case is designed to serve the iPhone users who like to travel light, without having to carry all sorts of things around with them. The wallet case allows iPhone users to leave their wallet or purse at home while keeping their cards, cash, or house key safely stored in the back of their iPhone. This case comes in Black, White, or Pink, and is currently available for the iPhone 4 and 4S, with an iPhone 5 model listed as coming soon. The Holda iPhone Wallet Case is available for purchase for $34.95.

•  Quad Lock - iPhone Bike Mount

As the name suggests, the Quad Lock iPhone bike mount is designed for cyclists, allowing users to securely attach their iPhone to their bike. The Quad Lock also comes with one advantage over other mounts: when disconnected from the bike, it can serve as a protective case for day to day use. This iPhone accessory is available in Black or Blue, works with the iPhone 4 and 4S, and an iPhone 5 model is also in the works. The Quad Lock iPhone Bike Mount is available for purchase for $69.95.

•  Quad Lock - iPhone Tripod Adaptor

While this iPhone accessory can prove useful to any iPhone user, its main fan base is likely among those constantly uploading iPhone pictures to Facebook and Instagram. The Tripod Adaptor allows iPhone users to securely mount their smartphone to any standard tripod with just a simple twist. It is designed to work well for video, low light, as well as time-lapse or panorama photo apps. It requires a Quad Lock iPhone case, and it only comes in black. The Quad Lock Tripod Adaptor is available for purchase for $19.95.