Yeah that app is a total nightmare for astro... been there, done that, never again. Honestly the T7 uses a 2.5mm sub-mini jack and you really want a dedicated intervalometer instead of just a basic trigger. If you wanna do 2 minute exposures, a simple button wont cut it because you'll be standing there holding it the whole time. For a 35 dollar budget, wired is 100% the move. Cold nights absolutely kill the tiny coin batteries in wireless remotes, and radio interference can be a pain in the middle of nowhere. Plus, wired ones just dont have lag. Heres why a wired intervalometer is better for Joshua Tree:

• It handles the specific timing for you so you dont have to count in your head.
• You can set it to take 20 shots in a row with 5 second gaps if you want to stack them later.
• Zero battery drain on the camera from keeping the wifi active.
• It has a locking button for bulb mode. I usually suggest the JJC TM-A LCD Timer Remote Shutter for Canon E3 because it is cheap and reliable. Another solid choice is the Neewer LCD Timer Shutter Release for Canon Rebel T7. Both should be way under your budget. Just make sure the cable has the 2.5mm plug. Once you plug it in, set the T7 to bulb mode and let the remote do the heavy lifting... its way more relaxing than fighting with a phone screen in the dark while your hands are freezing. Wait, did I mention the T7 uses the E3 connector? Yeah, dont buy the N3 one by mistake, that is for the 5D/7D series.

Jumping in here... honestly I learned the hard way that wireless remotes are just one more thing to go wrong when it is freezing at 2 AM. Spent years trying to get those perfect long exposures and nothing is worse than a dead battery in a transmitter right when the sky clears up. In my experience, going wired is the only way to feel 100 percent safe about your shots. Usually, I recommend staying away from the fancy wireless stuff for desert trips. Here is why I stick with a simple wired setup:

• It draws power directly so you dont have to worry about a transmitter dying mid-shot.
• Physical buttons are way easier to find by feel in the dark than a phone screen.
• You get a physical connection that doesnt drop like wifi or bluetooth does. Used the JJC TM-A LCD Timer Remote Shutter Release for ages and it is super reliable. Another one that works well is the Neewer Digital Timer Remote Shutter Release 2.5mm Jack... keeping it simple is the best way to not lose your mind out there in the dark.

Same setup here, love it