What are some alternatives?
When comparing Roost and PushCrew, you can also consider the following products
OneSignal - Customer engagement platform used by 800K+ developers; the fastest and most reliable way to send push notifications.
Pusher Push Notifications API - Send push notifications programmatically at scale
iZooto - Engage your mobile and desktop web users with intelligent web push notifications.
PushOwl - Re-engage website visitors with push notifications
Amazon Pinpoint - Targeted Push Notifications for Mobile Apps
Truepush - Free forever push notifications on Web and Mobile for everyone.