Pixate iOS helper for Xamarin.Forms. This class copies style info from Xamarin.Forms elements into the underlying native component.

StyledRenderer_iOS.cs

using System;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;
using YourProject.iOS;
using System.ComponentModel;
using MonoTouch.UIKit;
using MonoTouch.Foundation;
using PixateFreestyleLib;
using Common;

[assembly: ExportRenderer(typeof(Entry), typeof(StyledEntryRenderer))]
[assembly: ExportRenderer(typeof(Button), typeof(StyledButtonRenderer))]
[assembly: ExportRenderer(typeof(Image), typeof(StyledImageRenderer))]
[assembly: ExportRenderer(typeof(Label), typeof(StyledLabelRenderer))]
[assembly: ExportRenderer (typeof(ListView), typeof(StyledListViewRenderer))]
[assembly: ExportRenderer (typeof(ViewCell), typeof(StyledViewCellRenderer))]
[assembly: ExportRenderer (typeof(TextCell), typeof(StyledTextCellRenderer))]
[assembly: ExportRenderer (typeof(ImageCell), typeof(StyledImageCellRenderer))]
namespace YourProject.iOS
{
	public static class StyledRenderer {

		public static void UpdateStyle (UIView view, VisualElement model = null) {
			var styleId = model.StyleId;
			var classId = model.ClassId;
			UpdateStyle (view, styleId, classId);
		}

		public static void UpdateStyle (UIView view, string styleId, string classId) {
			if (!string.IsNullOrWhiteSpace (styleId)) {
				view.SetStyleId (styleId);
			}
			if (!string.IsNullOrWhiteSpace (classId)) {
				view.SetStyleClass(classId);
			}
			view.UpdateStylesNonRecursivelyAsync ();
		}

		public static void StyleOnHandlePropertyChanged (this NativeRenderer nr, object sender, PropertyChangedEventArgs e) {
			if (e.PropertyName == "ClassId" || e.PropertyName ==  "StyleId") {
				StyledRenderer.UpdateStyle (nr.Control, nr.Model);
			}
		}

		public static void StyleOnModelSet (this NativeRenderer nr, VisualElement model) {
			StyledRenderer.UpdateStyle (nr.Control, nr.Model);
		}
	}

	public class StyledEntryRenderer : EntryRenderer
	{	
		protected override void OnHandlePropertyChanged (object sender, PropertyChangedEventArgs e) {
			base.OnHandlePropertyChanged (sender, e);
			this.StyleOnHandlePropertyChanged (sender, e);
		}

		protected override void OnModelSet (VisualElement model) {
			base.OnModelSet (model);
			this.StyleOnModelSet (model);
		}
	}

	public class StyledButtonRenderer : ButtonRenderer
	{	
		protected override void OnHandlePropertyChanged (object sender, PropertyChangedEventArgs e) {
			base.OnHandlePropertyChanged (sender, e);
			this.StyleOnHandlePropertyChanged (sender, e);
		}

		protected override void OnModelSet (VisualElement model) {
			base.OnModelSet (model);
			this.StyleOnModelSet (model);
		}
	}

	public class StyledLabelRenderer : LabelRenderer
	{	
		protected override void OnHandlePropertyChanged (object sender, PropertyChangedEventArgs e) {
			base.OnHandlePropertyChanged (sender, e);
			this.StyleOnHandlePropertyChanged (sender, e);
		}

		protected override void OnModelSet (VisualElement model) {
			base.OnModelSet (model);
			this.StyleOnModelSet (model);
		}
	}

	public class StyledImageRenderer : ImageRenderer
	{	
		protected override void OnHandlePropertyChanged (object sender, PropertyChangedEventArgs e) {
			base.OnHandlePropertyChanged (sender, e);
			this.StyleOnHandlePropertyChanged (sender, e);
		}

		protected override void OnModelSet (VisualElement model) {
			base.OnModelSet (model);
			this.StyleOnModelSet (model);
		}
	}

	public class StyledListViewRenderer : ListViewRenderer
	{	
		protected override void OnHandlePropertyChanged (object sender, PropertyChangedEventArgs e) {
			base.OnHandlePropertyChanged (sender, e);
			this.StyleOnHandlePropertyChanged (sender, e);
		}

		protected override void OnModelSet (VisualElement model) {
			base.OnModelSet (model);
			this.StyleOnModelSet (model);
		}
	}
		
	public class StyledViewCellRenderer : ViewCellRenderer
	{
		public override UITableViewCell GetCell (Cell item, UITableView tv)
		{
			var cell = base.GetCell (item, tv);
			StyledRenderer.UpdateStyle (cell, item.StyleId, item.ClassId);
			return cell;
		}
	}

	public class StyledTextCellRenderer : TextCellRenderer
	{
		public override UITableViewCell GetCell (Cell item, UITableView tv)
		{
			var cell = base.GetCell (item, tv);
			StyledRenderer.UpdateStyle (cell, item.StyleId, item.ClassId);
			return cell;
		}
	}

	public class StyledImageCellRenderer : ImageCellRenderer
	{
		public override UITableViewCell GetCell (Cell item, UITableView tv)
		{
			var cell = base.GetCell (item, tv);
			StyledRenderer.UpdateStyle (cell, item.StyleId, item.ClassId);
			return cell;
		}
	}
}

OnModelSet has been deprecated in favor of OnElementChanged this needs to be switched out.

@jameymcelveen: This works great on iOS and I was wondering if you had a sample for Android.