Simplest/best way to control a set of 8-10 PWM signals from a smartphone As part of a larger project, I would like to be able to control a set of 8-10 PWM signals remotely, from a smartphone at a distance of 10 meters or more.  I will probably convert the PWM signals to analog voltages, and reduce their voltage swings to more like 0-1v, using a resistor divider and RC filter; they will drive high impedance loads in the remainder of the project.  I’d write an app for the smartphone allowing user control over the duty-cycle of each PWM signal (and thus the analog signal levels).

It seems to me that the way to go is Arduino, interfaced to the phone with Bluetooth.  I'd need one of the higher end Arduinos to get enough PWM signals (the basic ones like Uno only have 6 PWM outputs).  Software-generated PWMs are probably not high-frequency enough, as I’d like the filtered analog signals to be as ripple-free as possible. There seem to be several ways to interface Bluetooth to Arduino, such as the HC-05.

If people here concur with this approach, I shall move this question to the Arduino forum.

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HC-05 is rated to about 9m so it wouldn't necessarily meet your requirement. The ESP8266 (example of one implementation called the Node MCU) can output PWM on any of the 0-16 pins. It can easily implement a web server which would let you control your outputs via 8026.11 (wifi). It also means you don't need to build anything for the phone/ tablet/ PC just use a web browser. The duty cycle could be set through the web server on the ESP. The ESPs are around the same price as an Arduino.  

I've used the HC-05 with an arduino. It works very well, though not very far. For the Android side I used app inventor which is extremely easily to use for bluetooth.