I want to know if it is possible to build an app that can send alerts to others on ethereum blockchain.
If it's possible then how fast do you think the alerts can be sent and then received by the recipients?
There's the option to use a smart contract with events. It will allow everyone who follows your contract address to receive these events.
contract Tweet{
event Msg (string msg);
function makeTweet(string _msg) public {
Msg (_msg);
}
}
Pay attention, people will have to manually add your smart contract to their clients in order to receive these message.
No it's not, or the others will have to check manually the contract (or have an app that does it for them)