Yes Gary Seven was very similar to Doctor Who! In fact you could say he was a blueprint for Jon Pertwee's Doctor in the seventies except that the producers admitted that the inspiration for that era was more The Avengers and Quatermass than anything else before it returned to it's usual space travelling pattern in the ninth series in 72!
Man, it's a relief to see you say that. Usually people jump to the conclusion that Gary was based on
Who instead of the other way around, even though most of the
Who elements that are similar came along after "Assignment: Earth." (The sonic screwdriver was introduced within weeks of Gary's servo, but at the time, it was literally just a sonic screwdriver, not yet the multipurpose tool it would become later.) Indeed, A:E was originally developed as a non-Trek-related half-hour series in 1966, around the end of the Doctor's first incarnation, so even if Roddenberry could've somehow been aware of
Who at the time, he would've only been aware of it as the adventures of a heroic young man and a teenage girl who wandered through time and space with an elderly eccentric from the future and rarely spent any time on present-day Earth. It would've borne no resemblance to "Assignment: Earth" at that point.
Conversely, the format change that put the Doctor on present-day Earth, defending it against threats, was conceived in the Patrick Troughton era, before anyone in the UK could've seen "Assignment: Earth." The "pilot" for that new version of the series, "The Web of Fear," was broadcast a month before A:E aired in the US, and the plans had been in development even longer. So they just happened to develop independently. As
Greg Cox has remarked before, it's likely that they were both drawing on the high-tech spy craze of the era to some extent. There's an element of
The Day the Earth Stood Still to A:E as well.
I suppose that, since the sonic screwdriver didn't begin acquiring multiple functions until later seasons, it could conceivably have been influenced by Gary's servo. But it's more likely that they're just both sci-fi riffs on a Swiss Army knife. And aliens having a single tool that can do everything is a pretty common trope, if for no other reason than that it saves money on prop building. (See also the Kelvans' belt devices in "By Any Other Name," Korob's scepter in "Catspaw," the Vians' hand devices in "The Empath," even the tricorder to an extent. There are no doubt a few in
Who as well.)