The save the date invite reads, "A new conversation around health is about to begin. Be there when it starts". The event takes place May 28th in San Francisco.
Engadget notes that the invite came from Samsung's Semiconductor arm so it could be about forthcoming sensors and components.
Apple's WWDC runs from June 2nd to June 6th and the company is expected to unveil iOS 8 at the event. Whether the company will debut a new Healthbook app is still unclear as recent reports have suggested that some iOS 8 features could be pushed back or perhaps kept under wraps until the iPhone 6 launches later in the year.