Appearances by Facebook CEO Mark Zuckerberg and Viacom International Media Networks CEO Bob Bakish, buzz about latest gadgets and a focus on bringing more wireless gear and content to the developing world – they were all part of this year's Mobile World Congress in Barcelona, which took place this week.

Considered the world's largest event for the mobile industry, the MWC tends to see a slew of announcements and much debate. This year, some 72,000 attendees had registered for four days of product announcements, work meetings and schmoozing.

The holy grail of lasting energy sources was a key topic of debate as Ericsson and Philips signed an agreement to integrate small cells into street lighting and the Upp hydrogen fuel cell, which uses hydrogen to fully recharge an iPhone 5, was introduced.

Here is THR's look at some of the game changers and key take-aways from the 2014 edition of the mobile industry gathering in Spain.

Mark Zuckerberg says WhatsApp is worth even more than $16 billion

Zuckerberg’s opening keynote speech at the Congress was well attended. The timing seemed perfect after Facebook agreed the week before to acquire instant messaging service WhatsApp for $16 billion.

Zuckerberg surprised some attendees by saying that WhatsApp was already worth more than the $16 billion price tag. But he also set the tone of the Congress’ quest to tap into new markets by talking up his Internet.org initiative. It is designed as an “on ramp” to access consumers in developing countries, he told the crowd.

Also in Barcelona, WhatsApp CEO Jan Koum revealed that the messaging service would offer free calling to its 450 million users by the second quarter of this year.

Tablets, meet "phablets"!

"Phablets” mark a new trend in the industry to combine traditional smartphones with the viewability of tablet computers.

They are defined as phones with screens larger than 5 inches. Among the phablets on display in Barcelona were Samsung’s much-anticipated waterproof 5S, Sony’s Xperia Z2 and ZTE’s Grand Memo II, which offers extra long battery life and 16GB of internal memory. Yota's two-faced cell phone, with an e-reader on one side and a color 5-inch screen on the other also made quite a splash.

"It's a new type of gadget," creator Vladislav Martinov told journalists. "The problem with smartphones is that the screen is always dark when it sleeps, and it seems like a basic error to us."

Smartband watches and bracelets monitor physical activity and show messages and content

Sony, Samsung and Huawei all unveiled smartband watches and bracelets, which monitor physical activity on a curved, tactile screen that also shows messages, e-mails, music and videos. Looking to transform the cell-phone experience into an ever-niftier scenario, companies introduced wearable gear that connects via bluetooth to the handset.

Most of the bands trumpet sports-tracking features, like pedometers and sleep-cycle and heart-rate monitors, and some like Huawei's TalkBand have a popout earpiece for phone calls. 

Apple skipped the Mobile World Congress, as it has in past years, and left the industry intrigued as to whether it is working on an iWatch.

5G anyone?

While 4G was the center of attention, with speeds of 300 Mbps coming soon to many carriers, 5G is on the cusp of availability, with Huawei announcing it had exceeded 100 Gbps in tests in Barcleona. While understanding that 3G networks are for voice and data and 4G is expected to up broadband Internet connectivity, 5G would usher in the so-called Internet of Things.

The idea is that any device could talk to any other device. That would open the door for driverless cars and mobile health care by machines among other innovations.

But the immediate research stems more from the exponential growth of traffic each year, meaning the amount of spectrum now available will soon be insufficient.

"Four Years From Now" across town from the Congress looks into the future

One of the hottest things at the Mobile World Congress was actually across town, the spin-off known as "Four Years From Now" or 4YFN, where innovative startups introduced wearable gadgets like GPS for motorcycle helmets and promised to outdo the stalwarts with creativity in the short-term.

Former Telefonica Research and Development CEO Carlos Domingo, who recently announced his departure to Dubai, used the platform to talk about how the near future means people will no longer be limited to their five senses and benefit from the "10 senses" of mobile phones.

Some examples include glasses that augment reality, sensors that can integrate into people's bodies for health care benefits and cars that drive themselves.

"We are in the midst of a digital revolution, probably one of the most important ones in the industry for several decades," Domingo said.

This story originally appeared on THR.com.