I don't quite understand the idea of having these 2 products separated, or at least, not integrate one in the other for subscribers.
What's the sense of activity when you can't "directly" interact with it? you just have to check demo here, 80% of the posts is "logins"!
What I want to be able is to have an interactive wall!, like you can find in fb, g+ or even jomsocial, I can see the activities there, interact with them or add new ones. I don't have to swap tab to post something on my wall for it to appear in activities!
Please, consider doing it a single plugin, or develop activities further to include walls on it!