Bodybuilding, as its name pretty much implies, is all about gettin' big muscles. And while a tape measure can be used to measure the growth of those muscles every now and then, XLFLEX is designed to motivate users by providing them with ongoing real-time measurements as they're working out.

Developed by Texas-based startup Visual Gains, XLFLEX takes the form of a belt that is worn over the biceps, triceps, forearms, thighs or calves. While the user is pumping iron, a sensor in the sweat-proof device continually measures the changing circumference of that muscle. Measurement data (in a choice of inches or centimeters) is displayed on an integrated LCD screen, plus it's transmitted by Bluetooth to an iOS/Android app on the user's smartphone.

Depending on where the device is being worn, its LCD display can be electronically flipped over in order to appear rightside-up to the user. It can also be reversed, so it appears the right away around when viewed in a mirror, or it can simply be blanked out in order to keep prying eyes from seeing its numbers.

The app, meanwhile, not only lets users track their progress over time, but also allows them to set size goals for different muscles – it alerts them when those goals are met. Additionally, it's capable of monitoring multiple XLFLEX devices (worn on various parts of one user's body) simultaneously.

It should be noted that the product is intended for users who are already pretty far along the bodybuilding road, as its minimum arm-circumference size is 12 inches (30.5 cm). It maxes out at 25 inches (63.5 cm).

If you're interested, XLFLEX is currently the subject of a Kickstarter campaign. A pledge of US$135 will get you a single unit, assuming it reaches production. The planned retail price is $289.

The system is demonstrated in the following video.

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