Ten days ago we reported on how Slack, a messaging platform for internal company discussions, has begun to open itself to travel-related integrations.
As we noted, Tripnary was the first to use Slack to enable searches for flights from Skyscanner, the metasearch service.
Last night Kayak debuted a similar plug-in for Slack. This suggests that a new greenfield channel for gaining traffic has been discovered by travel companies.
You can add a Kayak widget to enable the integration. Simply type /kayak and your search request into the command line of Slack to see results. For instance:

/kayak a great hotel in las vegas july 1st to 6th
Encouraging such integrations is vital to Slack, as it tries to defend its lead as an enterprise messaging platform, which is being challenged by rivals like Quip, HipChat, Cisco's Spark, and IBM's Verse. But the real war may ultimately be against Facebook Messenger.
For Kayak's part, this is a natural fit, as the company's tech teams have become enamored with the Slack service.
As for Tripnary, it would like to remind people of its boast that it gives users the ability to search for destinations based on a set budget, something Kayak's tool doesn't yet do.
Lastly, another startup, Roomino, wants to say that its functionality lets you request hotels via Expedia (and eventually other sources) from Slack. It says it was the first to enable such integrations on the messaging service.
Update 12pm ET: Meekan, an Israeli startup, has been using Skyscanner's flights data for both Slack and Hipchat since the end of last year.
Earlier: In-app travel search continues, Slack fans can now find flights