Completely new to indoor cycling, is there a MUCH cheaper alternative to power meter that would be compatible with the RGT app? I'm planning to get a cheap, not-smart mag trainer, to cycle inside. I'm currently a stay-at home mom and I would like the cheapest, yet enjoyable app-wise, set up for indoor training with virtual riding. I really like what I read about RGT- no cost to use the app, BUT it seems like  you must have the equipment on the quite expensive end of the cost spectrum. Here is their site's compatibility explanation.
Am I right in this assessment? Is there some type of computer alternative to a power meter that you think could work with this app? I have NO idea what's out there apart from basic speed/cadence sensors which I cannot use for this app. I imagine that is because the virtual ride uses LOTS of specific data from your own ride to make it more realistic and awesome.
I imagine I will end up buying a basic speed sensor and use another app I have to pay for. (Yuck to paying a monthly price for an app. I'm super cheap). Before going that route, I wanted to see if there was any type of alternative buy that may pay for itself over the course of x number of months if I use RGT  as a free app vs. paying monthly for an app. I'm also happy to hear any opinions about the following apps which seem to have the journey cycling feel I would enjoy: Ful Gaz,Rouvy, Bkool, Zwift, another unknown to me, etc.
About my cycling, if it is relevant:  I am a casual cyclist who enjoys leisurely, outdoor cycling and I often seek out new trails. Before I was a mom, I did do longer rides (30-55 mi) so I think I will actually cycle indoors especially if I have a virtual path, BUT I am definitely not a hard-core cyclist trying to get best times. I'm not even looking for an especially tough work-out, although I am competitive in general and would be motivated most by a &quot;self-competition&quot;- something where I could see previous time on same course, etc. But on the whole,  I simply want to enjoy getting exercise regularly inside and, the kicker.... I would like to do it for about as cheap as possible.
You can basically use any trainer with a powermeter (I would call it a &quot;smart trainer&quot; but others do protest too much). The cheapest ones start at 200€, better ones, with a more accurate power meter, say 300€. There is no need to have a powermeter on your bike. These trainers are not that much more expensive than the copletely dumb ones. You are looking for Bluetooth or ANT+ connections. A powertmeter in atrainer is easier to make than a bicycle poweemeter and hence much cheaper. Bicycle powermeters cost as much as a whole trainer.
&quot;Smart&quot; trainers, or trainers with a powermeter in general, normally calculate the power you are performing against the brake automatically. Some are more accurate, some are less accurate. Some virtual competitions require only certain more accurate devices. But for a smart trainer you do NOT have to measure the speed of your wheel and have the RTG or Rouvy or Zwift or whatever other app to calculate your power from your wheel revolution speed. The trainer is calibrated and is giving you the estimate from its own powermeter - more accurate or less accurate, but its own automatic estimate nonetheless.
Also you do not need a subscription-based app for training with a smart trainer. A basic app is normally included and if not, there are alternatives available. It normally includes various power-based exercise programs.
You only need subscription for advanced features, especially for virtual rides and online riding with other people, for special training programs and related.
I won't do any product recommendation, there are many products. Some are using a wheel driven by your rear tyre (the basic ones), some have their own axle and cassette and you connect it instead of your rear wheel (direct drive). They use different braking mechanism (hydraulic, magnetic...) and differ in the level of noise and many other factors. You have to do some research yourself.
Weiwen Ng linked a nice survey of trainers https://www.dcrainmaker.com/2019/10/the-smart-trainer-recommendations-guide-winter-2019-2020.html You can do a web search and fine many other reviews and surveys.