Breeders are still hard at work on that one. Among the recent introductions is Passion Mix, a dwarf that is available as seed. It has flowers in purple, rose, and white. In 1999 it was chosen as an All-American Selection. According to Thompson and Morgan, it's an easy seed to start.
Care is very straight-forward.
The plants are drought tolerant and require a sunny position for the flowers. If it gets shaded by other plants, flowers may not fully open, something I discovered when a taller plant cast its shadow over the calibrachoa. The flowers must be regularly dead-headed to prolong flowering. In repayment, you will enjoy up to 8 months of flowering. Osteospermums are generally trouble free plants.