Samsung has sent out press invitations to a special May 28 event in San Francisco where it promises "A new conversation about health is about to begin."

The invitation is intriguing for two reasons. The first being that it is scheduled just four days before Apple's WWDC where health and fitness are expected to be high on the agenda -- Apple is expected to unveil the Healthbook suite of apps at the event and might even offer a quick demo of an 'iWatch.'

But secondly, the event is a true surprise in that whatever Samsung is planning to reveal hasn't already been leaked.

That said, there are still a couple of clues. The invitation is from the company's semiconductor arm, suggesting a focus on sensors and capabilities more than hardware. But then there's the fact that Samsung has recently trademarked the product name "Galaxy S Fitness" in the US. So maybe another health-focused wearable is on the way.

The company has already been very busy in this regard. Since January it has launched three devices capable of motion and fitness tracking -- the Gear 2 smartwatch, the Gear 2 Neo smartwatch, and the Samsung Gear Fit smartband.

However, there's no way to be sure until May 28, when all will be revealed.