There are systems available already.
A Laserscanner - but that is quite a lot of extra weight
Or a software solution- as long as the database is updated properly.
I use the second system on an BK117D2 (Airbus H145) and the Helionix System works quite nice with first giving you a „Caution - Obstacle“ and shortly afterwards a „Waning - Obstacle“ and it works not only with powerlines but also with windcraft mills, chimneys (mostly grey painted and also sometimes hard to spot, when the lights are in cloud) and so on.
It even warns for terrain, when getting to low outside an airfield (and yes, it can be muted 😉
