Pushnotifications via Pushover
Using the easy to integrate service of Pushover (https://pushover.net/) push notifications could be a thing!
It would be additional to the website (Current deals) and the emails.
There are official clients for the following plattforms:
- iOS (iPad
- Chrome, Firefox, Safari/Mac OS X
And there is an unofficial client (https://github.com/cgrossde/Pullover) which is works as native client on Windows/Linux and Mac.
Since Pushover has some free API-limits, this would be a premium feature. 7500 notifications are free per month, additional notifications can be bought (10,000 for $50.00 USD, 25,000 for $115.00 USD, 50,000 for $200.00 USD).
An easy way to stay free would be to integrate Pushover in the user client (so that the users would have to use their own API key) or to use the e-mail gateway. The emails should be better formatted for the gateway.