AG introduced the AGU and I tried it for awhile. The subscription to it was something like $8 /mo. Included in that subscription was a subscription to the mag, and the online content. I don't know of any other mag that offers that kind of thing the way you are wanting.
While it was nice having that on my iPad, it really wasn't worth it for me, working out to about $96/yr just didn't seem a good thing, when I could get the mag for $19 /yr, and get some of the online content. The AGU stuff was not as good as other offerings available. Have you tried "On The Path"? I think that is great way to interface with online content.
Whoever is running the digital side of AG Mag needs help, or maybe vocational guidance. I've had two extremely frustrating interactions with AG support this week trying and failing to get the iPad app to recognize that I have a digital subscription. The support person I just talked to wasn't even aware that there is an iPad app. Both support people were so clueless that I gave up and cancelled my subscription.