If muscle tone is a major goal right now, you're on the right track with yoga. Of particular benefit are the poses that involve balance and extension. Achieving proper form in these positions takes a great deal of body awareness and muscle control, and holding these positions takes power. While specific poses, or asanas, should be integrated together into a cohesive yoga session, some of the poses that may best address your specific goals include:
Warrior I, II, or III
Downward facing Dog
In terms of other non-gym exercises that lead to muscle tone, consider some form of rock climbing or bouldering.
If theres not a lot of outdoor rock climbing to be done in your area, try a climbing gym. I realize you want to avoid gyms, but I believe the bigger issue you want to avoid is the dull repetition of lifting weights or running on a treadmill. You want to participate in activities that are enjoyable in their own right, not just means to an end. You may need to climb indoors because of where you live, but Id encourage you to try it, because you can continually challenge your skills and its an exercise that addresses your goals.
Other activities you may want to consider include squash and racquetball. These high-speed racket sports involve a great deal of powerful side-to-side, front-to-back running (typically its more lunging than running though) and theres a lot of twisting through the torso and use of the upper body for swinging the racket and maintaining balance. The best part about squash and racquetball is that the court is enclosed; you dont have to spend a lot of time retrieving poorly hit balls because they generally come back to within a few steps of you.