Hi,
I'm evaluating your grid and arising thereby some issues. I hope it's just because I'm unexperienced 
I use the Xamarin-Bindings (Xamarin.IOS / MonoTouch)
I have a simple ShinobiDataGrid with two Columns. Each use the CellType of "SDataGridTextCell". In the "SDataGridDelegate" I'm overriding the method "OnBeginEditingCell" with the following code:
var cell = grid.VisibleCellAtCoordinate(coordinate) as SDataGridTextCell;
var cellTextField = cell.TextField as SGridTextField;
cellTextField.InputView = new UITextView();
var viewController = new UIViewController();
var navBar = new UIToolbar(new RectangleF(0, 0, viewController.View.Bounds.Width, 50)) {BarStyle = UIBarStyle.Black, Translucent = true, Items = new[] { new UIBarButtonItem(UIBarButtonSystemItem.Done, (s, e) => {_popoverController.Dismiss(true);})}};
navBar.SizeToFit();
var textField = new UITextField(new RectangleF(0, 50, viewController.View.Bounds.Width, viewController.View.Bounds.Height)) { Placeholder = "Mein Text...", BackgroundColor = UIColor.White };
viewController.View.Add(navBar);
viewController.View.Add(textField);
_popoverController = new UIPopoverController(viewController);
_popoverController.SetPopoverContentSize(new SizeF(250, 200), false);
_popoverController.PresentFromRect(cell.Bounds, cell.TextField.Superview, UIPopoverArrowDirection.Any, false);
In this case I'm not able to set the focus directly to the TextField in the Popover to start entering text without tapping into the popover again. And I'd like to prevent the user to enter any text directly to the textfield. Something like readonly. But setting the cell.TextView.Enabled = false will be ignored in any case.
A tried out a second way to achieve a custom input. Therefore I set the InputView property of the cell.TextField. But the only thing happens is that neither the keyboard nor the custom input view appears.
I'm looking forward to get very soon an answer. 
Best regards,
Danny