The Seeker was a type of electronic flying device similar to a camera drone which was designed for covert surveillance and detection of enemy targets. They were developed by
Albert Wesker who then was part of the HCF, a rival to Umbrella - and were initially developed to assist
Hunter II B.O.W.s who had enough intelligence to accept orders and understand cues from the Seeker.
An enhanced version also existed which was militarised, later used by one of Albert Weskers underlings,
Jack Krauser during his mission in Spain, where he used them while in open combat with
Leon S. Kennedy, These had machine guns fitted to them, and there was another variety which was equipped with a bomb in which it would fly at the target kamikaze style.
Seekers were clearly not designed for combat as they could be destroyed with a single bullet anywhere in its chassis. They were far better suited for long range support operations. It's not clear if the Seeker was ever used again after these handful of operations, but as
Albert Wesker would eventually take front stage and attend the next operation himself, remote surveillance was no longer required.
Seekers first appeared in
Resident Evil Code: Veronica / X, and later in
Resident Evil 4.