A possible purchasable item would be a perimeter detection item, which you could place on the ground and it would ping you (and the map) when a unit passes through it. To keep it balanced, consider making it expire over time in some fashion. Possibly also have it be remotely deployable (like remote mine fields), maybe at an additional cost.
A possible purchasable item would be a perimeter detection item, which you could place on the ground and it would ping you (and the map) when a unit passes through it. To keep it balanced, consider making it expire over time in some fashion. Possibly also have it be remotely deployable (like remote mine fields), maybe at an additional cost.