They do have other options that you can add-on, such as electronic inspection reports, mailing services and e-lease (this one is included if you're a Pro member which I am not) but I haven't found the need for any of those services yet.  

A good way to do this is have it electronically signed the night before you meet with them to exchange money.

However, do make sure you have some form of electronic confirmation that their payment was received.

If the remediation devices intrude significantly into the livable space, that will probably detract from value. 

Hello, We don't currently have a STR, but posting here because many STR use these kinds of devices.   

I like that they have online electronic signatures and when you have 5-6 students on one lease it makes it more convenient to just email out the lease to each person for signature.  

Do you have both physical and electronic copies of all the necessary paperwork?

Finally, you could consider electronic locks where you change the codes between tenants.

Other states consider the "paid" date to be when the landlord receives the money for electronic payments. 

I would think a detection device would be easy to fool or disable, and difficult to prove in court.I would focus on inspections and look for the following evidence, then document with pictures, written warnings, demands of cleaning/repairs, and follow-up inspections.