Make your strength training or body-weight exercises more challenging by adding a balance element. Turn bilateral exercises unilateral. Instead of a regular deadlift, try a single leg deadlift. Instead of doing standing bicep curls, balance on one leg instead of two.
Last year I attended this workshop in Orlando. I have been training the active aging for the past 5 years. This workshop taught me how the BOSU® Balance Trainer can provide assistance, resistance, cushioning and stimulus to amplify the effect for this important market of exercisers.