You can do HTTP streaming, where clients access a resource of indefinite length. This should work well enough with native clients and even some modern browsers

You can do HTTP streaming, where clients access a resource of indefinite length. This should work well enough with native clients and even some modern browsers (with EventSource aka Server Sent Events, or streaming XmlHttpRequest). Long-polling with retries is not so bad though. Even with WebSockets you'd still want a periodic heartbeat. It's all the same amount of traffic really.