I don't remember if that's what they're actually called, but the little robots from ratchet and clank that you used to have a certain amount of into a gate, and it'd open something.
I could get a model of both, but i'd need somebody else to animate and export it, since i have no idea how this one works. i'll PM the .blend when i finish to whenever would like to animate and export.
They follow you around, and walk into the gate if they're close enough. They cannot jump.
The gate should have a changeable amount of bots required. they should probably be a vehicle, with some way to make it link to the action of something else when activated.
:3