For now to make it as universal as possible only browsers that support non subscription notifications are supported. I believe chrome though are working on this, so it should be supported soon.
Once notifications are more popular and adopted better by all browsers I will be adding in support for both types.
I'll be adding an update later this week to show a preview image and to also add sound.
Not sure about the page, it's not a major issue as it can still only be accessed by admins but I'll address that in the update.