QST did a terrible review of the Wavenode System. They mentioned the spectrum analyzer, but did not test its dynamic range or speed to see if its fast enough to act as a reliable splatter monitor.
The Wavenode web page does not give much reliable information on how good the system is. It would be nice if they placed a video on the page showing how fast it is.
Any SDR receiver is still the best spectrum analyzer that the average ham can afford. The better SDR receivers have spectrum analyzer performance that cannot be matched for price.
Any decent second receiver is another good choice, I do this routinely. I just park a receiver 5khz away while on the air. Its easy to hear any unusual IMD. This helped me to find a faulty balun which was hit by lighting, I could hear the fault before I even knew about it. The lightning damage balun caused horrendous TX imd problems that was evident on the second receiver.
I use scopes. But just for the 'Neat' factor. The best way to check my signal is free. I ask the operator on the other end. Sure, doesn't answer the splatter question, but you'd have to be overdriving any of the more modern equipment to enter into the 'Splatter Zone'.
I also use Wavenode WN-2 Watt Meters. The software has a spectrum analyzer and scope function built in. It uses samples from the bi-directional sensor to display your signal. This is another option that works very well. It also has other functionality that would warrant a visit to the site.