Not many alternatives that come close. But Zenprospect looks a good
For teams just getting started it might be a decent option. Would definitely test on a smaller scale for a while before rolling it out to teams of over 10 SDR's or AE's.
I've implemented it with every sales team I've managed, and recommend it to any founder I come across. I've been a fan since the beginning and will continue to support. Such a fantastic product!
feature rollout seems to have slowed down and almost all of the recent features seems to be salesforce focused.