Handslide opens your PDF and reads your camera only on this device — nothing is uploaded, no account. Voice commands use your browser's speech service, which may process the sound on the browser maker's server, and they don't work in Firefox. A browser can't control desktop PowerPoint: export the deck to PDF and present that (animations and transitions are lost in a PDF).
A browser presenter you drive by hand and by voice
Open a slide PDF and press Present. Swipe a hand, say “next” or press your clicker to move on.
Hand tracking runs on this device and downloads about 18 MB once, the first time. It works best in good light, 1–2 m from the camera, with a clear sideways sweep; after each turn it waits a moment (the cooldown) before taking the next gesture. The PDF is not kept, so open it again next time. iPhone browsers can't go full screen, so you get a view that fills the page instead.