I use the Timing and Scoring viewer as a non-subscriber.
When you get familiar with where the DRS zones are on each track (try asking the subscribers in your league while you're in the race; one will probably happily tell you), you can tell based on your sector times. Your time through the sector where the DRS zone is will typically be 0.3 to 0.7s quicker than normally, depending on how long the zone is.
From memory, these are the
DRS Zone Locations (DRS detection & activation line):
- Australia: front straight (exit of last corner)
- Malaysia: front straight (exit of last corner)
- China: back straight (just before Intermediate 2)
- Bahrain: front straight
- Spain: front straight (just before Start/Finish)
- Monaco: front straight
- Turkey: back straight (about 10 seconds down the road from Intermediate 2)
- Britain: Hangar Straight (just before Intermediate 1)
- Germany: back straight (about 5 seconds on from Intermediate 2)
- Hungary: front straight
- Europe: back straight (about 4 seconds on from Intermediate 1)
- Belgium: Kemmel Straight (entirely within Sector 1)
- Italy: front straight (exit of Parabolica)
- Singapore: back straight (exit of Turn 5)
- Japan: front straight (exit of Casio Triangle, just a couple hundred meters before Start/Finish)
- Brazil: front straight (just before the kink)
- Abu Dhabi: back straight (just before Intermediate 1)