Weekend gadget bag: 5 offbeat ideas

• SoBi app lets users reserve and locate bikes
• Increase data caps through social sharing with FreedomPop
• Zooka speakers upgrade audio from tablets

This week we're taking a look at offbeat tech gadgets, beginning with a spooky toy to complete your Halloween costume.

Add an audio component to your costume

Making its debut at New York Comic Con earlier this month, ThinkGeek's Mega Stomp Panic ($39.99) is the perfect finishing touch for a spine-tingling costume.

The accessory, which clips onto a belt or waistband, adds a level of audio reality to Halloween costumes. Using an accelerometer, the gadget creates sounds that are synchronized to your every step and stomp. With nine audio profiles, you can make that zombie, pirate or medieval knight costume (to name a few) come to life with sound. There's even a rainstorm mode, so if you're planning on dressing up as the creature from the black lagoon, you're covered. Every step will sound like you're slogging through rain puddles.

A 'smart' bike-sharing program

Car sharing has proven popular in major cities, driven by urbanites ready to give up auto ownership. But now one company's hoping to do the same with "smart" bikes.

SoBi (short for Social Bicycles) is a bike-sharing program powered by AT&T. Using a smartphone app, consumers can reserve, track, locate and unlock smart bikes that are equipped with GPS. The use of mobile technology creates a convenient system that lets users pick up and drop off bikes anywhere. SoBi will launch in three cities this fall, with more to come in 2013: San Francisco; Buffalo, N.Y.; and Sun Valley, Idaho.

More friends, more free 4G

If you're tired of sky-high mobile bills, a startup wants to give you free 4G data.

Stemming from the belief that Web access is a basic right (preach on!), FreedomPop tries to provide as free an experience as possible, offering social features to increase monthly data caps. You get 500MB to start and can earn more with each additional friend on the service or by completing partner offers, such as signing up for trial programs, playing online games or answering surveys. Even the devices are free: Both the hotspot device and USB stick require a deposit ($89 and $49, respectively) that are fully refundable when returned to the company. It is only when you exceed your free data limit that you start paying; each additional megabyte costs two cents.

Currently, FreedomPop has a beta program that uses Clearwire's 4G WiMAX network, which is limited in speed and coverage. Still, in San Francisco, I was able to achieve speeds of 7 Mbps downstream and 2 Mbps upstream — more than adequate for working while streaming Pandora. FreedomPop will transition to Sprint's LTE network in early 2013.

Zooka, a speaker companion for tablets

This unusual-looking Bluetooth speaker won't satisfy audiophiles, but it's a great accessory for tablet viewers tired of less-than-stellar sound from their devices.

For its size, Carbon Audio's Zooka ($99) outputs impressive audio, able to fill a small room (to my surprise). Like many Bluetooth speakers on the market, it also doubles as a speakerphone for calls. Ideal for streaming movies on a tablet, Zooka, which can last eight hours on a full charge, includes a slot to connect to laptops and tablets. On computers, it sits on the top of the screen; the speaker's design includes a small hole so it doesn't block Web cams. To enhance the tablet experience, Zooka doubles as a kickstand with a removable metal rod. With it, you can rest your iPad on the speaker to watch movies or video chat hands-free.

Pack protects gadgets and backs with air

While it won't win any prizes in a backpack beauty contest, Air Bac packs unique technology to keep gear safe and your body comfortable. As its name suggests, a built-in air cushion helps alleviate back stress by adjusting to different body types and the load of the bag. The company claims that this makes the weight on your back feel like half of what it actually is.

The backpacks come pre-filled with air, but it's recommended that owners adjust it to their comfort and pump it up once a year. Though its ($89.99) is on the bulky side, I have to admit that it's incredibly comfortable on the shoulders with its cushy straps, and my back isn't complaining either.

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E-mail Alice Truong at techcomments@usatoday.com. Follow her on Twitter:@alicetruong.