I hope this is the correct topic area.
I've been looking at a number of Simulators that allow people to create circuits, test them and with Arduino write code, etc. The 123D seems ok for an online solution, although it does not have some of the features that I got use to with other tools.
I also worry about Online tools and the ability for people to snoop on your projects. Not that I'm paranoid that someone is going to steal my billion dollar idea, but I'm worried that someone is going to steal my 10 dollar idea and turn it into a billion dollar product.
I would prefer a non-online solution, but don't want to plug up my computer with a bunch of demos that God Knows what they are loading on my VM.
Any recommendations. I don't mind spending a few bucks either. Like to support the developers when I can.
I wouldn't even worry about using a simulator - just use the Arduino itself.
Write your code, but instead of using the various "digitalWrite()", etc functions - serial print (or better, build your own library) the states as needed. For input (digital or analog), use another function that returns a value. Audio would be more problematic; you could likely just output a number or something (whatever would represent the waveform).
This serial stream - if designed properly (and actually, there's probably already a library out there that does this) could then be interfaced with Processing or something similar - to give you "virtual LEDs" and "virtual switches" and "virtual potentiometers" - etc - if you really need to twiddle things.
Otherwise, doing a bit of "blind coding", along with simple serial monitoring - will get you quite far in your projects before committing to real hardware - especially if you are needing this for "on the go" coding sessions. Also note that there are (or can be easily made) various simple "dongle" boards and such for LEDs and switches; in fact, you might be able to build your own "testing rig" using a pro-mini or nano, with some LEDs, buttons/switches, and a few potentiometers (and maybe a small speaker) - which could provide you with all the necessary debugging hardware needed.
Yes - you would still have to carry an Arduino or such with you - but it isn't like they are full-sized computers or anything.
Finally - note that simulators sometimes do a great job at what they are doing - so much so that when you take your simulated circuit and code, and build the real-world version - it doesn't work (or breaks in weird ways). This is generally just an effect of where a simulation runs in "ideal world" space - where everything is perfect - unlike real components and connections.
I'm not saying you should give up your simulator search quest - but just realize that you may not need one at all for most purposes...
This is good advice - I see what you mean.