I implemented some basic tooltips, which show (if defined) the label and value onmouseover.
Every tooltip can be registered by a configurable area:

Tooltip Defaults can be overwritten by adding a 2nd parameter to the "new Chart()" function, i.e.

var myChart = new Chart(context, { background: 'black', fontColor: 'white' });

tooltipDefaults = {
    background: 'rgba(0,0,0,0.6)',
    fontFamily : "'Arial'",
    fontStyle : "normal",
    fontColor: 'white',
    fontSize: '12px',
    padding: {
        top: 10,
        right: 10,
        bottom: 10,
        left: 10
    },
    offset: {
        left: 0,
        top: 0
    },
    border: {
        width: 0,
        color: '#000'
    }
}

The tooltip moves relative to the current mouse cursor position and shows only, if hovering a valid chart point or area.
Tooltips can be disabled via specific chart option "showTooltips" i.g.

myChart.Pie(pieChartData, { showTooltips: false });

They can be styled individually and do right now a basic job:
Showing the hovered label and value.