The new device will have a colour e-paper display and up to seven days battery life, the firm claimed.
It will also have a microphone enabling users to send short voice replies to notifications and messages received from the watch via their smartphone.
Pebble raised more than $10m (?6.4m) in crowdfunding for its first generation device.
It has since sold more than one million Pebble watches.
In the first hour following the announcement of Pebble Time more than $2m (?1.2m) had been raised by roughly 11,000 backers, smashing the device's initial fundraising target of $500,000 (?323,000).The new screen is colour e-paper.
"Pebble was first brought to life by 69,000 backers and people who supported our vision three years ago. We could not think of a better way to share our new watch," said Eric Migicovsky, chief executive of Pebble.
"With Pebble Time, we're launching completely new hardware and re-imagined software."
The new watch will be 20% thinner than its predecessor and comes with a smart accessories port which the firm hopes will encourage developers to build hardware for it.
A new operating system organises alerts chronologically - although the screen is not a touchscreen.
Pebble intends to ship the new watch to its crowdfunder backers at the end of May, and have it on sale worldwide by the end of the year with a retail price of $199 (?128).The device is said to be 20% thinner than its predecessor.
Some experts said that size was one factor affecting the smartwatch industry.
"It seems more intelligent but one problem will be readability under various light conditions," said watch expert Alexander Linz.
"I have to wear reading glasses - I couldn't read a watch without glasses.
"A mini screen with limited resolution will probably not have big success because it is hard to read - even the iPhone got bigger in the end."
Mr Linz added that future generations of smart watches were likely to come with Near Field Communication (NFC) tools, enabling the device to be more autonomous - which Pebble Time does not have.
"NFC will be the future," he said.
"Without it, take away the smartphone and ask yourself what is left. It's a mirror on your wrist mirroring information from your phone."