Grandmothers are wearing Fitbit, Jawbone bracelets pack the shelves of big-box stores and Apple's smartwatch is expected to be one of the most coveted Christmas gifts this year.

Wearable technology gadgets — which use Wi-Fi and come in the form of eyeglasses, bracelets, wristwatches and other small accessories for the body — have gone from nerdy and outlandish devices to popular purchases for the average consumer, a sign of how comfortable we have become with tracking our daily activities, whether it's how well we sleep or how many calories we burn.

Now entrepreneurs are working to push the technology to new heights, creating gadgets that don't simply collect data on the body but can alter the user's physical and mental state. Thync, a start-up based in the California San Francisco Bay Area town of Los Gatos, launched publicly last week with a device that sends electricity to the user's nerves to alter their mood and mental state.

The user has two options: become calmer or more energized. The mood-altering fix is delivered through a Bluetooth-connected headpiece, a strip attached to the neck or behind the ear to stimulate nerves that emerge directly from the brain, and a smartphone.

Mind and body manipulation can be scary terrain, but easy-to-use devices such as Fitbit have paved the way for wearables 2.0. With a growing market and explosion of new companies — not to mention the gorilla of consumer electronics storming onto the scene in April with the Apple Watch — companies such as Thync are looking to stand out from the crowd.

"All wearables today are trackers," said Thync co-founder and CEO Isy Goldwasser. "Our wearable is working in synergy with the body."

Thync has raised $13 million from investors including Khosla Ventures.