Call Bliss does work as advertised, though the user experience does need some TLC. To get started, follow the introductory tutorial. It's a hassle, as you have to jump back and forth between Call Bliss and the Settings app four times. That's not the developer's fault, as Call Bliss need certain iOS settings to be in place. I just wish it were handled more elegantly.
Once that's done, it's time to add a few allowed callers. Tap the Allowed screen and then tap "+Add". Call Bliss presents a sorted list of your contacts. This is one of the few screens that looks good. Tap any that you'd like to allow to pass through and then hit Done. They're now listed on the Allowed Callers screen.
You can also allow whole groups or go by location. This is the app's best feature. You can identify any location and determine which calls you're willing to receive and which should be blocked during your stay. Additionally, you can tell the app to block all calls while at a given location -- good if you'll be at a wedding, funeral, play, etc. -- or allow all calls. It's super-handy.
Here's a bit that's confusing. Call Bliss creates a separate list for contacts allowed at a certain location vs. those allowed globally. These lists appear one on top of the other on the Allowed Calls screen. Unfortunately, you can't edit both from the Allowed screen. Tapping the Edit button makes the global list editable, but not the location-based list. This threw me for a loop for a few minutes until I realized that I had to go to the Places screen and then tap the current place to edit that second list.
Also, if you have no global contacts allowed and only a few location-specific contacts, the Allowed screen doesn't make a clear distinction. It looks like the Edit button has just disappeared, though the Add button remains. I understand why it works that way, but the presentation is confusing.
The Options screen lets you set a global blackout mode to deny all calls or an "open door" mode to allow all calls. Here's another nit to pick: the tutorial shows the both the blackout slider and the open door slider set to "On." Of course, they can't both be on at the same time.
Finally, there's an in-depth help section built in. Unfortunately the formatting is off, many line breaks are in odd locations and there is no space between paragraphs, which makes it difficult to read the tiny text.
Call Bliss does what it says on the tin, and even improves upon Apple's currently malfunctioning Do Not Disturb. The location-specific settings are especially nice. Unfortunately, the unattractive and time-consuming tutorial, confusing elements, spelling errors and sparse UI prevent me from recommending it. Call Bliss is a great idea that's poorly executed. Hopefully a future update will allow this app to have the attention it deserves.