What OS are you trying to block? If users have the Windows Pulse client, they will not be able to login from the client in any way so Host Checker is not needed. If desired, yes, you can use a Host Checker file policy to prevent login if Pulse is installed or process check if it is running on the client machine and deny access if the policy evaluates to true.
If you are worried about iOS devices connecting, Host Checker is not available on that platform (as you are aware). You could put a restriction on the realm (Users>User Realms>realmName>Authentication Policy>Browser) that denies *Pulse* as the first rule and then an allow rule for *Windows*, *Mac*, *Linux*
