Samsung has officially announced the Galaxy S4 at its Radio City Music Hall event in New York City. JK Shin, Samsung's head of mobile communications, teased a number of the leaked features that we expected to hear and then finally introduced the new handset, which looks just like what we saw in earlier leaks. The phone will launch on 327 mobile operators in 55 countries starting at the end of April, with 3G and 4G / LTE versions available, and its polycarbonate case will initially be available in two colors, white and black.

The 5-inch screen features a 1080p resolution, as expected, is covered with Corning's Gorilla Glass 3, and it's known as a "full HD super AMOLED" screen with 441 pixels per inch. The phone comes with 802.11ac Wi-Fi (which also runs on the standard a/b/g/n bands), Bluetooth 4.0, and Cat 3 100 / 50 Mbps LTE, and also comes with an IR blaster like the HTC One. Key specs include a removable 2,600 mAh battery, 2GB of RAM, and 16, 32, or 64 GB of storage. Also of note is the new processor — either a Samsung Exynos 5 or Qualcomm Snapdragon S4 Pro 600 processor, depending on the region. (Update: we learned the day after Samsung's event that the Qualcomm processor Samsung is using was not the Snapdragon S4 Pro but the more powerful Snapdragon 600.)

Samsung is also touting its new 13-megapixel camera (the front camera is 2-megapixels), which the company says can take more than 100 shots in four seconds and then select some to composite into a single frame — the company says this will help eliminate photo bombs. It also has a "Sound and Shot" feature that lets you record five seconds of audio before you take a photo. Another unusual camera feature is the "dual camera" mode, which takes shots with both the front and back cameras and integrates them into a single scene.

There's a whole host of other new software features on top of the Android 4.2.2 Jelly Bean OS, as well. As rumored, there are a few eye-tracking features on board. "Smart Pause" lets you pause a video simply by looking away, with it resuming when you look back, while "Smart Scroll" lets you move through emails or web pages without looking at the screen — Samsung says the phone recognizes your face looking at the screen as well as the movement of your wrist and moves the content to match your movements.

One of the more interesting software additions is S Health — Samsung's clearly been paying attention to the wearable computing trends. The phone's sensors can monitor your fitness level and surroundings, making it a full-fledged fitness tracker — it'll integrate with a number of Samsung accessories, as well. The phone features a built-in pedometer for tracking the number of steps you take — or run — during the day, much like Fitbit's line of devices. However, sensors in the phone also allow it to measure the ambient temperature and humidity of the room you're, all of which feeds into the S Health app itself. Diet tracking is integrated as well, with the app pulling able to pull caloric information from a database of common food items.

Samsung also added some touch-free gestures to the Galaxy S4: Air View and Air Gesture. The former lets you hover your fingers over the screen to pull out contextual data or preview the content of messages, while the latter lets you control features like your music, answering calls, or scrolling without having to actually touch the screen. Samsung also debuted a couple of new accessories, including a new Xbox-like Bluetooth gaming controller and wireless charging cases, which support either the PMA or the Qi charging standard.

Overall, it's a rather shocking amount of new software and features — time will tell how much of this gains traction with users. There's no word on how much the Galaxy S4 will cost yet, but it'll be available in Q2 on Verizon, Sprint, T-Mobile, AT&T, US Cellular, and Cricket in the US. As for Europe, it'll be coming to carriers including Deutsche Telecom, EE, H3G, Orange, Telenor, Telia Sonera, Telefonica, and Vodafone.