If you can get a good, trusted brand for home CO monitors, I'd say go for it.
Apparently, Kidde is a trusted brand in fire alarms etc. in the US, so I think this one ($20) is probably equally trustworthy:
https://www.amazon.com/Kidde-Battery-Operated-Carbon-Monoxid...
I shudder to think that you would risk your life on a device of questionable quality.
The problem is surely knowing whether the expensive equivalent is just the same internals in a different retail pack (with other 'quality' signalling). That's genuinely hard for something that needs a lab to be tested.
There are a few companies that sell low level CO monitors for residential use. They're all somewhat pricey.
A CO monitor will set you back $235.
$235 sounds (relatively) expensive.
I recently replaced the 3 CO alarms in my flat - they cost me around £23 (29 USD) each [1].[1] http://www.toolstation.com/shop/Electrical/d190/Carbon+Monox...
Don't use a propane heater, please. It's dangerous to you and potentially to others nearby.
Source: Been there.