You're close on guessing microbiological research... I'm making beer. Home brewing is one of my hobbies and I thought it would be cool to measure the specific gravity (density relative to water) of the wort as it ferments. I wanted to have it on the outside of the fermenter to avoid contamination/infection. I suppose, if I could encase the sensors in stainless steel, I could sanitize it and drop it in but then I would have to worry about the signal propagating through the stainless. Maybe there's a reason I'm only finding medical ultrasound probes that are 1Mhz... 300 bucks too.
The ultrasonic tape measure is looking for the first reflected signal to calculate distance. I would ignore the first received signal because it would be from the glass.
I guess the only way to find out if it'll work is to just try it. If it doesn't work, It's only 50 bucks in parts total... if that.
I appreciate your help,
Matt