It is the regular Universal Orlando app. You have to select the HHN option from the menu then, once on the HHN page, click the map icon in the top right corner. After that, you have to zoom in on the resort and click on each individual house you want to see the wait time for (I have never seen a posted wait for AHS, though).
If anyone knows a simpler way, please do tell as this seems needlessly complicated compared to last year where we had a list that showed all the houses' wait times.
I have no idea how accurate the waits they have posted are as last night seemed rather light for crowds if the app was correct. Who was in the park last night that can tell me how on point the times were?