This app was mentioned in 23 comments, with an average of 1.78 upvotes
I've never used Glance for pebble, but from what I've read about it it looks pretty passive. It doesn't actually do much of anything on its own, it just displays data that gets sent to it (number of emails, texts, weather, etc).
Same goes for Music Boss. Since the pebble doesn't actually playback music on its own, it's at best acting as a remote control.
Apple Watch covers all of these use cases in "glances" which are different from actual apps. An "app" on Apple watch would be something like Maps, or Uber, or Instagram, or that garage-door opening thing they demoed in the keynote (with live video feed).
Surely you can understand that displaying a number of unread text messages is absolutely not on the same level as playing back a live video feed.
I'ts an app watchface. It can do little more than "ordinary" watchface :P Also there is couple styles in that app. I personally like ability to see all information on quick glance (pun not intented)
You can do all of those things very easily with any of the Pebble models.
You could download one of the existing watchfaces that other users have created, from the Pebble App Store. You can take a look at the Pebble app store here, on your web browser, via this emulator (click "Faces" button at the top to see watch faces!): http://pas.cpfx.ca
You could generate your own custom watchface, with no programming experience needed, using this awesome and very powerful, watchface generator too - right from your web browser! http://www.watchface-generator.de
If you have an Android Phone, you could generate a custom watchface with powerful features, right on your phone, using one of these two fantastic apps: Glance or Canvas
Lastly, if you have programming experience, you could code your own watchface or app using either the free SDK, in C or Java, or, using the cloudbased IDE - Cloud Pebble. See here: https://developer.getpebble.com
FYI, there's already a Pebble watchface named "Glance for Pebble".