Purchase the satellite locator upgrade with recovered salvage at any safehouse. Get a vehicle and drive around. When you get within range of a radio tag, a small pulsing green dot will appear on your map that will indicate the location of a missing tag.
The "Super Hammer" cheat requires 100 kills with the sledgehammer. To easily unlock it, go to dust near the chemical depot that is near the Badlands. Kill a few guards and go back out of the depot. Wait for cars to come by and take them from the civilians and the guerrillas. Form a wall using these cars with only two openings just big enough for people to fit through. Wait for the EDF to start coming in through the holes. Take out the sledgehammer and start bashing in heads. If they start trying to bash the car wall, blow up their cars. You can use the sledgehammer, but it will take awhile. Try using the explosives, because the kills do not have to be consecutive. Keep doing this until you have killed enough EDF.
Go to the oasis safehouse and turn around to find two non-EDF large explosive tanks. Shoot them from a safe distance and pick up the salvage. Use Guerrilla Express to travel to the oasis base and the tanks will be there again. Repeat for more salvage.
When you are around people, they will sometimes talk about Ultor, which is the company from Saints Row 2. They will also say "Damn drones confiscated my feed dogs collection", which is the band from Saints Row.
The area "Mt. Vogel" of Mars is a reference to Dean Vogel, whom you were required to kill in the last mission of Saints Row 2. You also only get to enter it during the final mission just before the campaign is complete.