Nebula is one of Anker's sub-brands, focused on making portable projectors. The Nebula Mars was its first product, a somewhat-large unit with dual JBL speakers and Android built-in. Normally it costs $599, but now you can get it for $449 from Amazon.
I reviewed this exact projector last month, and I came away mostly satisfied. Image quality is great, the speakers are loud, and the whole unit feels well-built. The major downside is the ancient version of Android 4.4 that it runs on. There's no Google Play Store either, so you'll have to download apps from the included third-party app store, or sideload APKs through the device's USB port.
If you want to do more than watch YouTube (without being able to log in), local videos, or Netflix, I recommend picking up a Chromecast. There's a full-size USB port on the back of the Mars (normally used for watching media from USB drives), so you can use a Chromecast/Fire TV Stick without plugging them into the wall. If you're still interested, you can buy it from the source link below.