The phrase "a key application for" is correct and usable in written English.
It can be used when discussing an important or significant use of a particular technology, method, or concept in a specific context.
Example: "Artificial intelligence has become a key application for improving customer service in various industries."
Alternatives: "a crucial use for" or "an essential application of".
"This also fits with the recent trend where Google piles into a market, gives away a key application for free, and forces the competition to respond".
Functional MRI (fMRI) benefits from both increased sensitivity and specificity with increasing magnetic field strength, making it a key application for Ultra-High Field (UHF) MRI scanners.
A key application for microsystems in life-science are active microimplants for restoring and substituting lost or impaired biological functions in humans.
A key application for ring rolled products used in turbomachinery and other engineering machines are components which take the form of a hollow truncated cone, or 'conical profile'.
In an individual analysis of each dataset we further showed that SIGACT and IBC differ markedly with regard to their usefulness for event timing analyses - a key application for both datasets.
A key application for a tool of this kind may lie in excluding patients at low risk of progression from enrollment into trials that evaluate management strategies initiated immediately after the diagnosis of AKI.
Large-scale analytics is a key application area for data processing and parallel computing research.
Web services––Web-accessible programs and devices––are a key application area for the Semantic Web.
Waste electrical and electronic equipment (WEEE) has become a key application area for extended producer responsibility (EPR).
However, Windows Phone remains especially small in its home market, the United States, a key application revenue source for iOS and Android developers.
A great case in point is a recent incident I've been made aware of at a Fortune 100 company in which a compliance director was informed that one of their company's IT vendors commented they were processing data for a key application in China.
